Liquid-crystalline medium and high-frequency components comprising same

ABSTRACT

The present invention relates to liquid-crystalline media comprising
         one or more chiral compounds and   one or more compounds selected from the group of compounds of formulae I, II and III,       

     
       
         
         
             
             
         
       
     
     in which the parameters have the meaning indicated in claim  1 , and to components comprising these media for high-frequency technology, in particular phase shifters and microwave array antennas.

FIELD OF THE INVENTION

The present invention relates to liquid-crystalline media and tohigh-frequency components comprising same, especially microwavecomponents for high-frequency devices, such as devices for shifting thephase of microwaves, in particular for microwave phased-array antennas.

Prior Art and Problem to be Solved

Liquid-crystalline media have a been used for some time inelectro-optical displays (liquid crystal displays: LCDs) in order todisplay information.

Recently, however, liquid-crystalline media have also been proposed foruse in components for microwave technology, such as, for example, in DE10 2004 029 429.1 A and in JP 2005-120208 (A).

As a typical microwave application, the concept of the invertedmicrostrip line as described by K. C. Gupta, R. Garg, I. Bahl and P.Bhartia: Microstrip Lines and Slotlines, 2^(nd) ed., Artech House,Boston, 1996, is employed, for example, in D. Dolfi, M. Labeyrie, P.Joffre and J. P. Huignard: Liquid Crystal Microwave Phase Shifter.Electronics Letters, Vol. 29, No. 10, pp. 926-928, May 1993, N. Martin,N. Tentillier, P. Laurent, B. Splingart, F. Huert, P H. Gelin, C.Legrand: Electrically Microwave Tunable Components Using LiquidCrystals. 32^(nd) European Microwave Conference, pp. 393-396, Milan2002, or in Weil, C.: Passiv steuerbare Mikrowellenphasenschieber aufder Basis nichtlinearer Dielektrika [Passively Controllable MicrowavePhase Shifters based on Nonlinear Dielectrics], DarmstädterDissertationen D17, 2002, C. Weil, G. Lüssem, and R. Jakoby: TunableInvert-Microstrip Phase Shifter Device Using Nematic Liquid Crystals,IEEE MTT-S Int. Microw. Symp., Seattle, Wash., June 2002, pp. 367-370,together with the commercial liquid crystal K15 from Merck KGaA. C.Weil, G. Lüssem, and R. Jakoby: Tunable Invert-Microstrip Phase ShifterDevice Using Nematic Liquid Crystals, IEEE MTT-S Int. Microw. Symp.,Seattle, Wash., June 2002, pp. 367-370, achieve phase shifter qualitiesof 12°/dB at 10 GHz with a control voltage of about 40 V therewith. Theinsertion losses of the LC, i.e. the losses caused only by thepolarisation losses in the liquid crystal, are given as approximately 1to 2 dB at 10 GHz in Weil, C.: Passiv steuerbareMikrowellenphasenschieber auf der Basis nichtlinearer Dielektrika[Passively Controllable Microwave Phase Shifters based on NonlinearDielectrics], Darmstädter Dissertationen D17, 2002. In addition, it hasbeen determined that the phase shifter losses are determined primarilyby the dielectric LC losses and the losses at the waveguide junctions.T. Kuki, H. Fujikake, H. Kamoda and T. Nomoto: Microwave Variable DelayLine Using a Membrane Impregnated with Liquid Crystal. IEEE MTT-S Int.Microwave Symp. Dig. 2002, pp. 363-366, June 2002, and T. Kuki, H.Fujikake, T. Nomoto: Microwave Variable Delay Line Using Dual-FrequencySwitching-Mode Liquid Crystal. IEEE Trans. Microwave Theory Tech., Vol.50, No. 11, pp. 2604-2609, November 2002, also address the use ofpolymerised LC films and dual-frequency switching-mode liquid crystalsin combination with planar phase shifter arrangements.

A. Penirschke, S. Müller, P. Scheele, C. Weil, M. Wittek, C. Hock and R.Jakoby: “Cavity Perturbation Method for Characterization of LiquidCrystals up to 35 GHz”, 34^(th) European Microwave Conference—Amsterdam,pp. 545-548 describe, inter alia, the properties of the known singleliquid-crystalline substance K15 (Merck KGaA, Germany) at a frequency of9 GHz.

A. Gaebler, F. Goelden, S. Müller, A. Penirschke and R. Jakoby “DirectSimulation of Material Permittivites using an Eigen-SusceptibilityFormula-tion of the Vector Variational Approach”, 12MTC2009—International Instrumentation and Measurement TechnologyConference, Singapore, 2009 (IEEE), pp. 463-467, describe thecorresponding properties of the known liquid-crystal mixture E7(likewise Merck KGaA, Germany).

DE 10 2004 029 429.1 A describes the use of liquid-crystal media inmicrowave technology, inter alia in phase shifters. It has alreadyinvestigated liquid-crystalline media with respect to their propertiesin the corresponding frequency range. In addition, it describesliquid-crystalline media which comprise a small amount of a singlecompound of the formula

respectively

in combination with the well known cyano biphenyl compound

and also media comprising, besides other compounds,

respectively

These relatively simple mixtures, however, show limited performance forthe application in devices operating in the microwave regime and evenneed to be significantly be improved with respect to their generalphysical properties, such as, especially, the clearing point, the phaserange, especially their stability against storage at low temperatures,and their viscosities, in particular their rotational viscosity.

Further liquid crystalline media for microwave applications comprisingone or more these compounds, as well as similar ones, are proposed byfor microwave applications in DE 10 2010 025 572 A and WO 2013/034227.

Polymer stabilization of liquid crystalline media, as well as doping bychiral dopants, has already been proposed for several types of displayapplications and for various reasons. However, there has been norespective suggestion for the type of applications envisaged by theinstant application.

The known devices for the high frequency-technology comprising thesemedia do still lack sufficient stability and, in particular, fastresponse.

However, these compositions are afflicted with serious disadvantages.Most of them result, besides other deficiencies, in disadvantageouslyhigh losses and/or inadequate phase shifts or inadequate materialquality.

For these applications, liquid-crystalline media having particular,hitherto rather unusual and uncommon properties or combinations ofproperties are required.

Novel liquid-crystalline media having improved properties are thusnecessary. In particular, the dielectric loss in the microwave regionmust be reduced and the material quality (η, sometimes also calledfigure of merit, short FoM), i.e. a high tunability and, at the sametime, a low dielectric loss, must be improved. Besides theserequirements increased focus has to be placed on improved response timesfor several envisaged applications especially for those devices usingplanar structures such as e.g. phase shifters and leaky antennas.

Polymer stabilization of liquid crystalline media, as well as doping bychiral dopants, has already been proposed for several types of displayapplications and for various reasons. However, there has been norespective suggestion for the type of applications envisaged by theinstant application.

The known devices for the high frequency-technology comprising thesemedia do still lack sufficient stability and, in particular, fastresponse.

However, these compositions are afflicted with serious disadvantages.Most of them result, besides other deficiencies, in disadvantageouslyhigh losses and/or inadequate phase shifts or inadequate materialquality.

But for several applications also the response times have to beimproved. This is obvious from the following. In the respectivecopmponents operating in the microwave regime, such as cavities andplanar structures, such as micro strip antennas, typically use a liquidcrystal material with a relatively large thickness. This thickness has adimension of about 50 μm to about 250 μm, which would be an extremelylarge cell gap for an LCD. Typically the switching time of liquidcrystals e.g. in electro-optical devices is proportional to the squareof the cell gap (d²). This results in relatively long switching times of1 to 2 minutes for a typical liquid crystal at ambient temperature.

In the field of liquid crystals it is well known to add a chiral dopante.g. into a nematic liquid crystal host mixtures. At low concentrationsof the chiral dopant a chiral-nematic phase, also called a cholestericphase is obtained. Increased concentrations are used in order to achievea higher degree of the chirality of the nematic phase required e.g. insuper twist LCDs. At very high concentrations highly chiral media areobtained, which may even exhibit so called blue phases, which have acubic orientational structure and are optically isotropic.

In electro-optical devices a general tendency of a decrease of theresponse time for switching off (τ_(off)) with increasing concentrationof a chiral dopant is expected as disclosed e.g. in U.S. Pat. No.4,141,947.

However, using chiral dopants in a nematic host in a higherconcentration generally leads to optical effects in the opticalspectrum, which may be desired or unwanted depending on the envisagedapplication. Most typical is the selective reflection of the cholestericliquid crystals having a cholesteric pitch in the respective region.This effect is highly undesired in most applications of liquid crystalsfor electro-optical decices and in severe cases even limit their use insuch applications.

While these effects in most cases negatively influence the operation ofelectro-optical devices they are not of that much concern for theperformance of RF components operating in the microwave region based onliquid crystals.

Another aim of the invention is to extend the pool of suitable materialsavailable to the expert. Other aims are immediately evident to theexpert from the following description.

Surprisingly, it has now been found that by using a chiral additive alsofrequently called a chiral dopant, respectively of one, two or morechiral additives, the response times and especially the “switching offtimes” (abbrev. τ_(off)) of the media in the devices can besignificantly reduced compared to the state of the art.

Preferably the chiral dopants present in the media according to theionstant application are mesogenic compounds and most preferably theyexhibit a mesophase on their own.

Particularly preferred the media according to the present inventioncomprise one or more chiral dopants. Preferably these chiral dopantshave an absolute value of the helical twisting power (short:HTP) in therange of 1 μm⁻¹ or more to 150 μm⁻¹ or less, preferably in the rangefrom 10 μm⁻¹ or more to 100 μm⁻¹ or less. In case the media comprise atleast two, i.e. two or more, chiral dopants, these may have mutuallyopposite signs of thier HTP-values. This condition is preferred for somespecific embodiments, as it allows to compensate the chirality of therespective compounds to some degree and, thus, may be used to compensatevarious temperature dependent properties of the resulting media in thedevices. Generally, however, it is preferred that most, or, even morepreferred, all of the chiral compounds present in the media according tothe present invention have the same sign of their HTP-values.

It has to be noted here that, as a first approximation, the HTP of amixture of chiral compounds, i.e. of conventional chiral dopants, aswell as of chiral reactive mesogens, may be approximated by the additionof their individual HTP values weighted by their respectiveconcentrations in the medium.

In this embodiment, the cholesteric pitch of the modulation medium inthe cholesteric phase, also referred to as the chiral nematic phase, canbe reproduced to a first approximation by equation (1).

P=(HTP·c)⁻¹  (1)

-   -   in which P denotes the cholesteric pitch,        -   c denotes the concentration of the chiral component (A) and        -   HTP (helical twisting power) is a constant which            characterises the twisting power of the chiral substance and            depends on the chiral substance (component (A)) and on the            achiral component (B).

If the pitch is to be determined more accurately, equation (1) can becorrespondingly modified. To this end, the development of thecholesteric pitch in the form of a polynomial (2) is usually used.

P=(HTP·c)⁻¹+(α₁ ·c)⁻²+(α₂ ·c)⁻³+ . . .  (2)

-   -   in which the parameters are as defined above for equation (1)        and α₁ and α₂ denote constants which depend on the chiral        component (A) and on the achiral component (B).

The polynomial can be continued up to the degree, which enables thedesired accuracy.

Typically the parameters of the polynomial (HTP (sometimes also calledα₁, α₂, α₃ and so forth) do depend more strongly on the type of thechiral dopant, and, to some degree, also on the specific liquid crystalmixture used.

Obviously, they do also depend on the enantiomeric excess of therespective chiral dopant. They have their respective largest absolutevalues for the pure enantiomers and are zero for racemates. In thisapplication the values given are those for the pure enantiomers, havingan enantiomeric excess of 98% or more, unless explicitly staedotherwise.

If the chiral component (A) consists of two or more compounds, equation(1) is modified to give equation (3).

P=[Σ _(i)(HTP(i)·c _(i))]⁻¹  (3)

in which P denotes the cholesteric pitch,

-   -   c_(i) denotes the concentration of the i-th compound of the        chiral component (A) and    -   HTP(i) denotes the HTP of the i-th compound of the chiral        component (A) in the achiral component (B).

The temperature dependence of the HTP is usually represented in apolynomial development (4), which, however, for practical purposes oftencan be terminated already right after the linear element (β₁).

HTP(T)=HTP(T ₀)+β₁·(T−T ₀)+β₂·(T−T ₀)²+ . . .  (4)

-   -   in which the parameters are as defined above for equation (1)        and        -   T denotes the temperature,        -   T₀ denotes the reference temperature,        -   HTP(T) denotes the HTP at temperature T,        -   HTP(T₀) denotes the HTP at temperature T₀ and        -   β₁ and β₂ denote constants which depend on the chiral            component (A) and on the achiral component (B).

In addition, there is a steady demand for an improvement in thelow-temperature behaviour of the components. Both an improvement in theoperating properties at low temperatures and also in the shelf life arenecessary here.

There is therefore a considerable demand for liquid-crystalline mediahaving suitable properties for corresponding practical applications.

The invention additionally has the aim of providing improved methods andmaterials, to achieve polymer stabilised mesogenic phases, in particularnematic phases, which do not have the above-mentioned disadvantages ofmethods and materials described in prior art. These mesogenic phasescomprise a polymer and a low molecular weight mesogenic material.Consequently, they are also called “composite systems”, or short“systems”.

Another aim of the invention is to extend the pool of suitable materialsavailable to the expert. Other aims are immediately evident to theexpert from the following description.

Additionally, it has been found that by using an RM, a stabilised liquidliquid crystalline phase which has improved, faster switching times,good tunability and acceptable loss can be achieved.

Additionally to mesogenic monomers the use of non-mesogenic monomers,such as 2-ethylhexylacrylate, is also possible and in certain instancesmyay be beneficial. It, however, also may be problematic due to thevolatile nature of such compounds, leading to problems of loss due toevaporation and inhomogeniety of the mixed monomer/host system.

Also, the use of non-mesogenic compounds can severely lower the clearingpoint of the liquid liquid crystalline host, leading to a much smallerwidth of the polymer stabilised nematic phase, which is not desirablefor most practical applications.

Using RMs having a cyclohexylene core instead of a core comprising oneor more 1,4-phenylenes has an advantage for the stability against UVirradiation in general and in particular against the UV irradiation usedin the polymerisation process. The resultant polymer stabilised phase(composite system) therefore has a high voltage holding ratio (VHR).

Also, it has been found that by using cyclohexylene RMs in combinationwith a liquid liquid crystalline host comprising fluorophenyl liquidliquid crystalline compounds, the RMs do effectively stabilise this hostto give a high VHR, which is necessary for advanced state-of-the-artdevices.

Present Invention

Surprisingly, it has now been found that it is possible to achieveliquid-crystalline media having a suitably fast switching times, asuitable, nematic phase range and loss which do not have thedisadvantages of the prior-art materials, or at least only do so to aconsiderably reduced extent.

These improved liquid-crystalline media in accordance with the presentinvention comprise

-   -   one or more chiral compounds    -   one or more compounds selected from the group of compounds of        formulae I, II and Ill

in which

-   R¹ denotes H, unfluorinated alkyl or unfluorinated alkoxy having 1    to 17, preferably having 3 to 10, C atoms or unfluorinated alkenyl,    unfluorinated alkenyloxy or unfluorinated alkoxyalkyl having 2 to    15, preferably 3 to 10, C atoms, preferably alkyl or unfluorinated    alkenyl,-   n denotes 0 or 1, preferably 1, and

-   -   independently of one another, denote

-   -   alternatively denotes

-   -   preferably

preferably

-   -   independently of one another, denote

more preferably

denotes

denotes

denotes

in which

-   R² denotes H, unfluorinated alkyl or unfluorinated alkoxy having 1    to 17, preferably having 3 to 10, C atoms or unfluorinated alkenyl,    unfluorinated alkenyloxy or unfluorinated alkoxyalkyl having 2 to    15, preferably 3 to 10, C atoms, preferably alkyl or unfluorinated    alkenyl,-   Z²¹ denotes trans-CH═CH—, trans-CF=CF— or —C≡C—, preferably —C≡C— or    trans-CH═CH—, and

-   -   independently of one another, denote

preferably

-   -   independently of one another, denote

preferably denotes

preferably denotes

-   -   more preferably

in which

-   R³ denotes H, unfluorinated alkyl or unfluorinated alkoxy having 1    to 17, preferably having 3 to 10, C atoms or unfluorinated alkenyl,    unfluorinated alkenyloxy or unfluorinated alkoxyalkyl having 2 to    15, preferably 3 to 10, C atoms, preferably alkyl or unfluorinated    alkenyl,-   one of Z³¹ and Z³², preferably Z³²; denotes trans-CH═CH—,    trans-CF=CF— or —C≡C— and the other one, independently thereof,    denotes trans-CH═CH—, trans-CF=CF— or a single bond, preferably one    of them, preferably Z³²; denotes —C≡C— or trans-CH═CH— and the other    denotes a single bond, and

-   -   independently of one another, denote

alternatively independently denotes e

preferably

-   -   independently of one another, denote

more preferably

denotes e

denotes e

and

-   -   more preferably

denotes e

-   -   more preferably

and

-   -   optionally one or more compounds of formula P

P^(a)—(Sp^(a))_(s1)-(A¹-Z¹)_(n1)-A²-Q-A³-(Z⁴-A⁴)_(n2)-(Sp^(b))_(s2)-P^(b)  P

wherein the individual radicals have the following meanings:

-   P^(a), P^(b) each, independently of one another, are a polymerisable    group,-   Sp^(a), Sp^(b) each, independently of one another, denote a spacer    group,-   s1, s2 each, independently of one another, denote 0 or 1,-   n1, n2 each, independently of one another, denote 0 or 1, preferably    0,-   Q denotes a single bond, —CF₂O—, —OCF₂—, —CH₂O—, —OCH₂—, —(CO)O—,    —O(CO)—, —(CH₂)₄—, —CH₂CH₂—, —CF₂—CF₂—, —CF₂—CH₂—, —CH₂—CF₂—,    —CH═CH—, —CF=CF—, —CF=CH—, —(CH₂)₃O—, —O(CH₂)₃—, —CH═CF—, —C≡C—,    —O—, —CH₂—, —(CH₂)₃—, —CF₂—, preferably —CF₂O—,-   Z¹, Z⁴ denote a single bond, —CF₂O—, —OCF₂—, —CH₂O—, —OCH₂—,    —(CO)O—, —O(CO)—, —(CH₂)₄—, —CH₂CH₂—, —CF₂—CF₂—, —CF₂—CH₂—,    —CH₂—CF₂—, —CH═CH—, —CF=CF—, —CF=CH—, —(CH₂)₃O—, —O(CH₂)₃—, —CH═CF—,    —C≡C—, —O—, —CH₂—, —(CH₂)₃—, —CF₂—, where Z¹ and Q or Z⁴ and Q do    not simultaneously denote a group selected from —CF₂O— and —OCF₂—,-   A¹, A², A³, A⁴    -   each, independently of one another, denote a diradical group        selected from the following groups:    -   a) the group consisting of trans-1,4-cyclohexylene,        1,4-cyclohexenylene and 1,4′-bicyclohexylene, in which, in        addition, one or more non-adjacent CH₂ groups may be replaced by        —O— and/or —S— and in which, in addition, one or more H atoms        may be replaced by F,    -   b) the group consisting of 1,4-phenylene and 1,3-phenylene, in        which, in addition, one or two CH groups may be replaced by N        and in which, in addition, one or more H atoms may be replaced        by L,    -   c) the group consisting of tetrahydropyran-2,5-diyl,        1,3-dioxane-2,5-diyl, tetrahydrofuran-2,5-diyl,        cyclobutane-1,3-diyl, piperidine-1,4-diyl, thiophene-2,5-diyl        and selenophene-2,5-diyl, each of which may also be mono- or        polysubstituted by L,    -   d) the group consisting of saturated, partially unsaturated or        fully unsaturated, and optionally substituted, polycyclic        radicals having 5 to 20 cyclic C atoms, one or more of which        may, in addition, be replaced by heteroatoms, preferably        selected from the group consisting of        bicyclo[1.1.1]pentane-1,3-diyl, bicyclo[2.2.2]octane-1,4-diyl,        spiro[3.3]heptane-2,6-diyl,

-   -    where, in addition, one or more H atoms in these radicals may        be replaced by L, and/or one or more double bonds may be        replaced by single bonds, and/or one or more CH groups may be        replaced by N,    -   and A³, alternatively may be a single bond,

-   L on each occurrence, identically or differently, denotes F, Cl, CN,    SCN, SF₅ or straight-chain or branched, in each case optionally    fluorinated, alkyl, alkoxy, alkylcarbonyl, alkoxycarbonyl,    alkylcarbonyloxy or alkoxycarbonyloxy having 1 to 12 C atoms,

-   R⁰³, R⁰⁴ each, independently of one another, denote H, F or    straight-chain or branched alkyl having 1 to 12 C atoms, in which,    in addition, one or more H atoms may be replaced by F,

-   M denotes —O—, —S—, —CH₂—, —CHY¹— or —CY¹Y²—, and

-   Y¹ and Y² each, independently of one another, have one of the    meanings indicated above for R⁰, or denote Cl or CN, and one of the    groups Y¹ and Y² alternatively denotes —OCF₃, preferably H, F, Cl,    CN or CF₃,    as well as to a polymer stabilized system obtainable by    polymerisation of one or more compounds of formula P alone or in    combination with on or more further polymerisable compounds from a    respective mixture, and to the use of such a stabilized system in    compomnents or devices for high frequency technology.

The chiral compounds of chiral component (A) preferably have a highabsolute value of the HTP. They are also referred to as chiral dopantssince they are generally added in relatively low concentrations tomesogenic base mixtures. They preferably have good solubility in theachiral component (B). They do not impair the mesogenic orliquid-crystalline properties of the mesogenic medium, or only do so toa small extent, so long as the cholesteric pitch has small values whichare much smaller than the wavelength of the light. If the cholestericpitch is in the order of the wavelength of the light and the temperatureis within a defined range, however, they induce a blue phase having acompletely different structure to that of the cholesteric phase. If twoor more chiral compounds are employed, they may have the same oropposite direction of rotation and the same or opposite temperaturedependence of the twist.

Particular preference is given to chiral compounds having an HTP of 20μm⁻¹ or more, in particular of 40 μm⁻¹ or more, particularly preferablyof 70 μm⁻¹ or more, in the commercial liquid-crystal mixture MLC-6828from Merck KGaA.

In a preferred embodiment of the present invention, the chiral component(A) consists of two or more chiral compounds which all have the samesign of the HTP.

The temperature dependence of the HTP of the individual compounds may behigh or low. The temperature dependence of the pitch of the medium canbe compensated by mixing compounds having different temperaturedependence of the HTP in corresponding ratios.

For the optically active component, a multiplicity of chiral dopants,some of which are commercially available, is available to the personskilled in the art, such as, for example, cholesteryl nonanoate,R/S-811, R/S-1011, R/S-2011, R/S-3011, R/S-4011, B(OC)2C*H—C-3 or CB15(all Merck KGaA, Darmstadt).

Particularly suitable dopants are compounds which contain one or morechiral radicals and one or more mesogenic groups, or one or morearomatic or alicyclic groups which form a mesogenic group with thechiral radical.

Suitable chiral radicals are, for example, chiral branched hydrocarbonradicals, chiral ethanediols, binaphthols or dioxolanes, furthermoremono- or polyvalent chiral radicals selected from the group consistingof sugar derivatives, sugar alcohols, sugar acids, lactic acids, chiralsubstituted glycols, steroid derivatives, terpene derivatives, aminoacids or sequences of a few, preferably 1-5, amino acids.

Preferred chiral radicals are sugar derivatives, such as glucose,mannose, galactose, fructose, arabinose and dextrose; sugar alcohols,such as, for example, sorbitol, mannitol, iditol, galactitol or anhydroderivatives thereof, in particular dianhydrohexitols, such asdianhydrosorbide (1,4:3,6-dianhydro-D-sorbide, isosorbide),dianhydromannitol (isosorbitol) or dianhydroiditol (isoiditol); sugaracids, such as, for example, gluconic acid, gulonic acid and ketogulonicacid; chiral substituted glycol radicals, such as, for example, mono- oroligoethylene or propylene glycols, in which one or more CH₂ groups aresubstituted by alkyl or alkoxy; amino acids, such as, for example,alanine, valine, phenylglycine or phenylalanine, or sequences of from 1to 5 of these amino acids; steroid derivatives, such as, for example,cholesteryl or cholic acid radicals; terpene derivatives, such as, forexample, menthyl, neomenthyl, campheyl, pineyl, terpineyl,isolongifolyl, fenchyl, carreyl, myrthenyl, nopyl, geraniyl, linaloyl,neryl, citronellyl or dihydrocitronellyl.

Suitable chiral radicals and mesogenic chiral compounds are described,for example, in DE 34 25 503, DE 35 34 777, DE 35 34 778, DE 35 34 779and DE 35 34 780, DE 43 42 280, EP 01 038 941 and DE 195 41 820.

Chiral compounds preferably used according to the present invention areselected from the group consisting of the formulae shown below.

Particular preference is given to dopants selected from the groupconsisting of compounds of the following formulae A-I to A-III:

in which

-   R^(a11) and R^(a12), independently of one another, are alkyl,    oxaalkyl or alkenyl having from 2 to 9, preferably up to 7, carbon    atoms, and R^(a11) is alternatively methyl or alkoxy having from 1    to 9 carbon atoms, preferably both are alkyl, preferably n-alkyl,-   R^(a21) and R^(a22), independently of one another, are alkyl or    alkoxy having from 1 to 9, preferably up to 7, carbon atoms,    oxaalkyl, alkenyl or alkenyloxy having from 2 to 9, preferably up to    7, carbon atoms, preferably both are alkyl, preferably n-alkyl,-   R^(a31) and R^(a32), independently of one another, are alkyl,    oxaalkyl or alkenyl having from 2 to 9, preferably up to 7, carbon    atoms, and R^(a11) is alternatively methyl or alkoxy having from 1    to 9 carbon atoms, preferably both are alkyl, preferably n-alkyl.

Particular preference is given to dopants selected from the groupconsisting of the compounds of the following formulae:

Further preferred dopants are derivatives of the isosorbide, isomannitolor isoiditol of the following formula A-IV:

in which the group

is

(dianhydrosorbitol),

(dianhydromannitol), or

(dianhydroiditol), preferably dianhydrosorbitol,and chiral ethanediols, such as, for example, diphenylethanediol(hydrobenzoin), in particular mesogenic hydrobenzoin derivatives of thefollowing formula A-V:

including the (R,S), (S,R), (R,R) and (S,S) enantiomers, which are notshown,in which

-   -   are each, independently of one another, 1,4-phenylene, which may        also be mono-, di- or trisubstituted by L, or 1,4-cyclo        hexylene,

-   L is H, F, Cl, CN or optionally halogenated alkyl, alkoxy,    alkylcarbonyl, alkoxycarbonyl or alkoxycarbonyloxy having 1-7 carbon    atoms,

-   c is 0 or 1,

-   Z₀ is —COO—, —OCO—, —CH₂CH₂— or a single bond, and

-   R⁰ is alkyl, alkoxy, alkylcarbonyl, alkoxycarbonyl or    alkylcarbonyloxy having 1-12 carbon atoms.

The compounds of the formula A-IV are described in WO 98/00428. Thecompounds of the formula A-V are described in GB-A-2,328,207.

Very particularly preferred dopants are chiral binaphthyl derivatives,as described in WO 02/94805, chiral binaphthol acetal derivatives, asdescribed in WO 02/34739, chiral TADDOL derivatives, as described in WO02/06265, and chiral dopants having at least one fluorinated bridginggroup and a terminal or central chiral group, as described in WO02/06196 and WO 02/06195.

Particular preference is given to chiral compounds of the formula A-VI

in which

-   X¹, X², Y¹ and Y² are each, independently of one another, F, Cl, Br,    I, CN, SCN, SF₅, straight-chain or branched alkyl having from 1 to    25 carbon atoms, which may be monosubstituted or polysubstituted by    F, Cl, Br, I or CN and in which, in addition, one or more    non-adjacent CH₂ groups may each, independently of one another, be    replaced by —O—, —S—, —NH—, NR⁰—, —CO—, —COO—, —OCO—, —OCOO—,    —S—CO—, —CO—S—, —CH═CH— or —C≡C— in such a way that O and/or S atoms    are not bonded directly to one another, a polymerisable group or    cycloalkyl or aryl having up to 20 carbon atoms, which may    optionally be monosubstituted or polysubstituted by halogen,    preferably F, or by a polymerisable group,-   x¹ and x² are each, independently of one another, 0, 1 or 2,-   y¹ and y² are each, independently of one another, 0, 1, 2, 3 or 4,-   B¹ and B² are each, independently of one another, an aromatic or    partially or fully saturated aliphatic six-membered ring in which    one or more CH groups may be replaced by N atoms and one or more    non-adjacent CH₂ groups may be replaced by O and/or S,-   W¹ and W² are each, independently of one another,    —Z¹-A¹-(Z²-A²)_(m)-R, and one of the two is alternatively R¹ or A³,    but both are not simultaneously H, or

-   U¹ and U² are each, independently of one another, CH₂, O, S, CO or    CS,-   V¹ and V² are each, independently of one another, (CH₂)_(n), in    which from one to four non-adjacent CH₂ groups may be replaced by O    and/or S, and one of V¹ and V² and, in the case where

both are a single bond,

-   Z¹ and Z² are each, independently of one another, —O—, —S—, —CO—,    —COO—, —OCO—, —O—COO—, —CO—NR⁰—, —NR⁰—CO—, —O—CH₂—, —CH₂—O—,    —S—CH₂—, —CH₂—S—, —CF₂—O—, —O—CF₂—, —CF₂—S—, —S—CF₂—, —CH₂—CH₂—,    —CF₂—CH₂—, —CH₂—CF₂—, —CF₂—CF₂—, —CH═N—, —N═CH—, —N═N—, —CH═CH—,    —CF=CH—, —CH═CF—, —CF=CF—, —C≡C—, a combination of two of these    groups, where no two O and/or S and/or N atoms are bonded directly    to one another, preferably —CH═CH—COO—, or —COO—CH═CH—, or a single    bond,-   A¹, A² and A³ are each, independently of one another, 1,4-phenylene,    in which one or two non-adjacent CH groups may be replaced by N,    1,4-cyclohexylene, in which one or two non-adjacent CH₂ groups may    be replaced by O and/or S, 1,3-dioxolane-4,5-diyl,    1,4-cyclohexenylene, 1,4-bicyclo[2.2.2]octylene,    piperidine-1,4-diyl, naphthalene-2,6-diyl,    decahydronaphthalene-2,6-diyl or    1,2,3,4-tetrahydronaphthalene-2,6-diyl, where each of these groups    may be monosubstituted or polysubstituted by L, and in addition A¹    is a single bond,-   L is a halogen atom, preferably F, CN, NO₂, alkyl, alkoxy,    alkylcarbonyl, alkoxycarbonyl or alkoxycarbonyloxy having 1-7 carbon    atoms, in which one or more H atoms may be replaced by F or Cl,-   m is in each case, independently, 0, 1, 2 or 3, and-   R and R¹ are each, independently of one another, H, F, Cl, Br, I,    CN, SCN, SF₅, straight-chain or branched alkyl having from 1 or 3 to    25 carbon atoms respectively, which may optionally be    monosubstituted or polysubstituted by F, Cl, Br, I or CN, and in    which one or more non-adjacent CH₂ groups may be replaced by —O—,    —S—, —NH—, —NR⁰—, —CO—, —COO—, —OCO—, —O—COO—, —S—CO—, —CO—S—,    —CH═CH— or —C≡C—, where no two O and/or S atoms are bonded directly    to one another, or a polymerisable group.

Particular preference is given to chiral binaphthyl derivatives of theformula A-VI-1

in particular those selected from the following formulae A-VI-1a toA-VI-1c:

in which ring B and Z° are as defined for the formula A-IV, and

-   R⁰ as defined for formula A-iV or H or alkyl having from 1 to 4    carbon atoms, and-   b is 0, 1 or 2,-   and Z⁰ is, in particular, —OCO— or a single bond.

Particular p reference is furthermore given to chiral binaphthylderivatives of the formula A-VI-2

in particular those selected from the following formulae A-VI-2a toA-VI-2f:

in which R⁰ is as defined for the formula A-VI, and X is H, F, Cl, CN orR⁰, preferably F.

Polymerisable compounds of formula P preferably used according to thepresent invention are selected from the group consisting of thefollowing formulae:

in which L in each occurrence, identically or differently, has one ofthe meanings indicated above and below, r denotes 0, 1, 2, 3 or 4, sdenotes 0, 1, 2 or 3, and n denotes an integer between 1 and 24,preferably between 1 and 12, very particularly preferably between 2 and8, and in which, if a radical is not indicated at the end of a single ordouble bond, it is a terminal CH₃ or CH₂ group.

In the formulae P1 to P24,

preferably denotes a group selected from the group consisting of thefollowing formulae:

particularly preferably selected from

The group A²-Q-A³ preferably denotes a group of the formula

in which at least one of the rings is substituted by at least one groupL=F. r here is in each case, independently, preferably 0, 1 or 2.

P^(a) and P^(b) in the compounds of formula P and the sub-formulaethereof preferably denote acrylate or methacrylate, furthermorefluoroacrylate.

Sp^(a) and Sp^(b) in the compounds of formula P and the sub-formulaethereof preferably denote a radical selected from the group consistingof —(CH₂)_(p1)—, —(CH₂)_(p1)—O—, —(CH₂)_(p1)—O—CO— and—(CH₂)_(p1)—O—CO—O— and mirror images thereof, in which p1 denotes aninteger from 1 to 12, preferably from 1 to 6, particularly preferably 1,2 or 3, where these groups are linked to P^(a) or P^(b) in such a waythat 0 atoms are not directly adjacent.

Of the compounds of formula P, particular preference is given to thosein which

-   -   the radicals P^(a) and P^(b) are selected from the group        consisting of vinyloxy, acrylate, methacrylate, fluoroacrylate,        chloroacrylate, oxetane and epoxide groups, particularly        preferably acrylate or methacrylate groups,    -   the radicals Sp^(a) and Sp^(b) are selected from the group        consisting of —(CH₂)_(p1)—, —(CH₂)_(p1)—O—, —(CH₂)_(p1)—O—CO—        and —(CH₂)_(p1)—O—CO—O— and mirror images thereof, in which p1        denotes an integer from 1 to 12, preferably from 1 to 6,        particularly preferably 1, 2 or 3, and where these radicals are        linked to P^(a) or P^(b) in such a way that 0 atoms are not        directly adjacent, Compounds of formula P preferably used        according to a preferred embodiment of the instant invention are        those comprising exactly two rings (n1=n2=0), which are        preferably 6-membered rings. Especially preferred are compounds        selected from the group of compounds of the following formulae:

wherein P^(a), P^(b), Sp^(a), Sp^(b), s1 and s2 are as defined underformula P above, and preferably Sp^(a/b) is alkylene —(CH₂)_(n)— whereinn preferably is 3, 4, 5, 6 or 7 and P^(a/b) preferably a methacrylat- oracrylate moiety. Especially preferred is the use of compounds selectedfrom the group of formulae Pa, Pb, Pc, Pd, Pe, Pf, Pg, Ph and Pi and, inparticular the compounds of formula Pa.

In formula P the moiety “A²-Q-A³” preferably is a moiety of formula

wherein preferably at least one of the two phenylene rings issubstituted by at least one L, which is different from H, wherein r isindependently for each ring, and preferably it is for each ring 0, 1 or2.

For the compounds of formula P, as well as for its respectivesub-formulae, preferably

P^(a) and P^(b) are, independently from each other, acrylate ormethacrylate, but also fluoroacrylate,

Sp^(a) and Sp^(b) are, independently from each other, —(CH₂)_(p1)—,—(CH₂)_(p1)—O—, —O—(CH₂)_(p1)—, —(CH₂)_(p1)—O—CO—, —CO—O—(CH₂)_(p1)—,—(CH₂)_(p1)—O—CO—O— or —(CH₂)_(p1)—O—CO—O—, wherein p1 is an integerfrom 1 to 12, preferably from 1 to 6, particularly preferred 1, 2 or 3,and wherein these moieties are linked with P^(a) or P^(b) in such a waythat no O-atoms are linked directly to on another.

Especially preferred is the use of compounds of formula P, wherein

-   -   P^(a) and P^(b) are vinyleoxy-, acrylate-, methacrylata-,        fluoroacrylate-, chloroacrylate-, oxetane- or an epoxygroup,        particularly preferred acrylate- or methacrylate,    -   Sp^(a) and Sp^(b) are —(CH₂)_(p1)—, —(CH₂)_(p1)—O—,        —O—(CH₂)_(p1)—, —(CH₂)_(p1)—O—CO—, —CO—O—(CH₂)_(p1)—,        —(CH₂)_(p1)—O—CO—O— or —(CH₂)_(p1)—O—CO—O—, wherein p1 is an        integer from 1 to 12, preferably from 1 to 6, particularly        preferred 1, 2 or 3, and wherein these moieties are linked with        P^(a) or P^(b) in such a way that no O-atoms are linked directly        to on another.

Suitable and preferred co-monomers for use in polymer precursors forpolymer stabilised devices according to the present invention areselected, for example, from the following formulae:

wherein the parameters have the following meanings:

-   P¹ and P² each, independently of one another, a polymerisable group,    preferably having one of the meanings given above or below for    P^(a), particularly preferred an acrylate, methacrylate,    fluoroacrylate, oxetane, vinyloxy- or epoxy group,-   Sp¹ and Sp² each, independently of one another, a single bond or a    spacer group, preferably having one of the meanings given above or    below for Sp^(a), particularly preferred an —(CH₂)_(p1)—,    —(CH₂)_(p1)—O—, —(CH₂)_(p1)—CO—O— or —(CH₂)_(p1)—O—CO—O—, wherein p1    is an integer from 1 to 12, and wherein the groups mentioned last    are linked to the adjacent ring via the 0-atom,-   and, wherein alternatively also one or more of P¹-Sp¹- and P²—Sp²-    may be R^(aa), provided that at least one of P¹—Sp¹- and P²—Sp²-    present in the compound is not R^(aa),-   R^(aa) H, F, Cl, CN or linear or branched alkyl having 1 to 25    C-atoms, wherein one or more non-adjacent —CH₂— groups,    independently of each another, may be replaced by —C(R⁰)═C(R⁰⁰)—,    —C≡C—, —N(R⁰)—, —O—, —S—, —CO—, —CO—O—, —O—CO—, —O—CO—O— in such a    way that neither O- nor S-atoms are directly linked to one another,    and wherein also one or more H-atoms may be replaced by F, Cl, CN or    P¹-Sp¹-, particularly preferred linear or branched, optionally    single- or polyfluorinated, alkyl, alkoxy, alkenyl, alkinyl,    alkylcarbonyl, alkoxycarbonyl, or alkylcarbonyloxy having 1 to 12    C-atoms, wherein the alkenyl- and alkinyl groups have at least two    and the branched groups have at least three C-atoms,-   R⁰, R⁰⁰ each, at each occurrence independently of one another, H or    alkyl having 1 to 12 C-atoms,-   R^(y) and R^(z) each, independently of one another, H, F, CH₃ or    CF₃,-   Z¹ —O—, —CO—, —C(R^(y)R^(z))—, or —CF₂CF₂—,-   Z² and Z³ each, independently of one another, —CO—O—, —O—CO—,    —CH₂O—, —OCH₂—, —CF₂O—, —OCF₂—, or —(CH₂)_(n)—, wherein n is 2, 3 or    4,-   L at each occurrence independently of one another, F, Cl, CN, SCN,    SF₅ or linear or branched, optionally mono- or polyfluorinated,    alkyl, alkoxy, alkenyl, alkinyl, alkylcarbonyl, alkoxycarbonyl,    alkylcarbonyloxy or alkoxycarbonyloxy having 1 to 12 C-atoms,    preferably F,-   L′ and L″ each, independently of one another, H, F or Cl,-   r 0, 1, 2, 3 or 4,-   s 0, 1, 2 or 3,-   t 0, 1 or 2, and-   x 0 or 1.

Suitable and preferred co-monomers for use in devices according to thepresent application operable and/or operating at a temperature where themesogenic medium is in the blue are for example selected from the groupof mono-reactive compounds, which are present in the precursor of thepolymer stabilised systems in a concentration in the range from 1 to 9wt.-%, particularly preferred from 4 to 7 wt.-%. Preferred mono-reactivecompounds are the compounds of formulae M1 bis M29, wherein one or moreof P¹-Sp¹- and P²-Sp²- are Rest R^(aa), such that the compounds have asingle reactive group only.

Particularly preferred mono-reactive compounds are the compounds of thefollowing formulae

wherein P¹, Sp′ and R^(aa) have the respective meanings given above andP¹ preferably is acrylate (CH₂=CH—CO—O—) or methacrylate(CH₂=C(CH₃)—CO—O—).

Amongst these the compounds of formula

wherein

-   n is an integer, preferably an even integer, in the range from 1 to    16, preferably from 2 to 8,-   m is an integer in the range from 1 to 15, preferably from 2 to 7,    are especially preferred.

Particular preference is given to an LC medium, an LC device, preferablyfor the high frequency technology, in particular for a phase shifter ora microwave antenna e.g. a leaky antenna, a process or the use asdescribed above and below, in which the LC medium or the polymerisableor polymerised component present therein comprises one or more compoundsof the following formula:

in which P^(a), P^(b), Sp^(a), Sp^(b), s1, s2 and L have the meaningsindicated above and below, r denotes 0, 1, 2, 3 or 4, and Z² and Z³each, independently of one another, denote —CF₂—O— or —O—CF₂—,preferably Z² is —CF₂—O— and Z³ is —O—CF₂— or vice versa or Z² is —CO—O—and Z³ is —O—CO— or vice versa, and, most preferably, Z² is —CF₂—O— andZ³ is —O—CF₂— or Z² is —CO—O— and Z³ is —O—CO—.

Preferably the liquid-crystalline media used according to the presentinvention comprise as a polymer precursor or part of a polymer percursorone, two or more reactive mesogens, referably one or more mono-reactivemesogens and, at the same time, one or more direactive mesogens.Optionally one or more of the reactive mesogens may be replaced by anon-mesogenic, respectively an isotropic, reactive compound, preferablyselected from HDMA, HDDMA, EHA, EA, EMA and the like.

In a preferred embodiment of the instant application theliquid-crystalline media used according to the present inventioncomprise a polymer obtained or obtainable by polymerisation, preferablyphotopolymerisation of a polymer precursor comprising one, two or morereactive mesogens, referably one or more mono-reactive mesogens and, atthe same time, one or more direactive mesogens. Optionally one or moreof the reactive mesogens may be replaced by a non-mesogenic,respectively an isotropic, reactive compound, preferably selected from2-ethylhexyl acrylate (EHA), 1,3,3-trimethylhexyl acrylate (TMHA),hexanolediacrylate (HDDA), hexanoledimethacrylate (HDDMA), and the like,but also from metylmethacrylate (MMA), ethylacrylate (EA),ethylmethacrylate (EMA) and 6-(4′-cyanobiphenyl-4-yloxy)hexyl acrylate(6CBA), a mesogenic monomer.

Preferably one or more, most preferably all, mono-reactive mesogens aremethacrylates and, also p referably one or more, most preferably all,mono-reactive mesogens are selected from the group of the bisacrylatesand the mixed acrylates-methacrylates, preferably they are bisacrylates.

Preferably the liquid-crystalline media according to the presentinvention comprise

-   -   one or more compounds of formula I and    -   one or more compounds of formula II        or    -   one or more compounds of formula I and    -   one or more compounds of formula III or    -   one or more compounds of formula II and    -   one or more compounds of formula III        or, most preferably,    -   one or more compounds of formula I and    -   one or more compounds of formula II and    -   one or more compounds of formula III.

In a preferred embodiment of the present invention, theliquid-crystalline media comprise one or more compounds of formula I andone or more compounds of formula III.

In a further preferred embodiment of the present invention, theliquid-crystalline media comprise one or more compounds of formula I andone or more compounds of formula II.

The liquid-crystalline media in accordance with the present inventionlikewise preferably comprise one or more compounds of formula II and oneor more compounds of formula III.

Particular preference is given in accordance with the present inventionto liquid-crystalline media which comprise one or more compounds offormula I, one or more compounds of formula II and one or more compoundsof formula III.

Additionally the liquid-crystalline media used according to the presentinvention in a certain embodiment preferably comprise one or morecompounds of formula IV,

in which

denotes

preferably

particularly preferably

-   L⁴ denotes alkyl having 1 to 6 C atoms, cycloalkyl having 3 to 6 C    atoms or cycloalkenyl having 4 to 6 C atoms, preferably CH₃, C₂H₅,    n-C₃H₇ (—(CH₂)₂CH₃), i-C₃H₇ (—CH(CH₃)₂), cyclopropyl, cyclobutyl,    cyclohexyl, cyclopent-1-enyl or cyclohex-1-enyl, and particularly    preferably CH₃, C₂H₅, cyclopropyl or cyclobutyl,-   x⁴ denotes H, alkyl having 1 to 3 C atoms or halogen, preferably H,    F or Cl, and particularly preferably H or F and very particularly    preferably F,-   R⁴¹ to R⁴⁴, independently of one another, denote unfluorinated alkyl    or unfluorinated alkoxy, each having 1 to 15 C atoms, unfluorinated    alkenyl, unfluorinated alkenyloxy or unfluorinated alkoxyalkyl, each    having 2 to 15 C atoms, or cycloalkyl, alkylcycloalkyl,    cycloalkenyl, alkylcycloalkenyl, alkylcycloalkylalkyl or    alkylcyclo-alkenylalkyl, each having up to 15 C atoms, and    alternatively one of R⁴³ and R⁴⁴ or both also denote H,    preferably-   R⁴¹ and R⁴², independently of one another, denote unfluorinated    alkyl or unfluorinated alkoxy, each having 1 to 7 C atoms, or    unfluorinated alkenyl, unfluorinated alkenyloxy or unfluorinated    alkoxyalkyl, each having 2 to 7 C atoms,    particularly preferably-   R⁴¹ denotes unfluorinated alkyl having 1 to 7 C atoms or    unfluorinated alkenyl, unfluorinated alkenyloxy or unfluorinated    alkoxyalkyl, each having 2 to 7 C atoms, and    particularly preferably-   R⁴² denotes unfluorinated alkyl or unfluorinated alkoxy, each having    1 to 7 C atoms, and    preferably-   R⁴³ and R⁴⁴ denote H, unfluorinated alkyl having 1 to 5 C atoms,    unfluorinated cycloalkyl or cycloalkenyl having 3 to 7 C atoms,    unfluorinated alkylcyclohexyl or unfluorinated cyclohexylalkyl, each    having 4 to 12 C atoms, or unfluorinated alkylcyclohexylalkyl having    5 to 15 C atoms, particularly preferably cyclopropyl, cyclobutyl or    cyclohexyl, and very particularly preferably at least one of R⁴³ and    R⁴⁴ denotes n-alkyl, particularly preferably methyl, ethyl or    n-propyl, and the other denotes H or n-alkyl, particularly    preferably H, methyl, ethyl or n-propyl.

Preferably the liquid crystal media contain one or more chiral dopantspreferably having an absolute value of the helical twisting power (HTP)of 20 μm⁻¹ or more, preferably of 40 μm⁻¹ or more, more preferably inthe range of 60 μm⁻¹ or more, most preferably in the range of 80 μm⁻¹ ormore to 260 μm⁻¹ or less.

The liquid-crystalline media in accordance with the present applicationpreferably comprise in total 5% to 70%, preferably 5% to 60% andparticularly preferably 30% to 50%, of compounds of formula I.

The liquid-crystalline media in accordance with the present applicationpreferably comprise in total 20% to 80%, preferably 30% to 70% andparticularly preferably 35% to 65%, of compounds of formula II.

The liquid-crystalline media in accordance with the present applicationpreferably comprise in total 5% to 45%, preferably 10% to 40% andparticularly preferably 15% to 35%, of compounds of formula III.

In a preferred embodiment of the present invention, in which theliquid-crystalline media comprise in each case one or more compounds offormulae I, II and III, the concentration of the compounds of formula Iis preferably 45% to 100%, preferably 50% to 100% and particularlypreferably 55% to 100%,

The concentration of the compounds of formula II is preferably 1% to20%, preferably 2% to 15% and particularly preferably 3% to 10%, and theconcentration of the compounds of formula III is preferably 1% to 30%,preferably 5% to 25% and particularly preferably 5% to 20%.

In a further preferred embodiment of the present invention, in which theliquid-crystalline media comprise in each case one or more compounds ofthe formulae I, II and III, the concentration of the compounds offormula I is preferably 15% to 40%, preferably 20% to 35% andparticularly preferably 25% to 30%, the concentration of the compoundsof formula II is preferably 10% to 35%, preferably 15% to 30% andparticularly preferably 20% to 25% and the concentration of thecompounds of formula III is preferably 25% to 50%, preferably 30% to 45%and particularly preferably 35% to 40%.

In a preferred embodiment of the present invention, in which theliquid-crystalline media comprise in each case one or more compounds ofthe formulae I and II, but at most 5% and preferably no compounds offormula III, the concentration of the compounds of formula I ispreferably 10% to 50%, preferably 20% to 40% and particularly preferably25% to 35% the concentration of the compounds of formula II ispreferably 40% to 70% preferably 50% to 65% and particularly preferably55% to 60%, and the concentration of the compounds of formula III ispreferably 1% to 4%, preferably 1% to 3% and particularly preferably 0%.

The liquid-crystalline media in accordance with the present applicationparticularly preferably comprise in total 50% to 80%, preferably 55% to75% and particularly preferably 57% to 70% of compounds of formula I-1and/or in total 5% to 70% preferably 6% to 50% and particularlypreferably 8% to 20% of compounds selected from the group of thecompounds of the formulae I-2 and I-3, most preferably compounds both offormula I-2 and of formula I-3.

The liquid-crystalline media in accordance with the present applicationlikewise preferably comprise in total 5% to 60% preferably 10% to 50%and particularly preferably 7% to 20% of compounds of formula II.

In the case of the use of a single homologous compound, these limitscorrespond to the concentration of this homologue, which is preferably2% to 20% particularly preferably 1% to 15%. In the case of the use oftwo or more homologues, the concentration of the individual homologuesis likewise preferably in each case 1% to 15%

The compounds of the formulae I to III in each case includedielectrically positive compounds having a dielectric anisotropy ofgreater than 3, dielectrically neutral compounds having a dielectricanisotropy of less than 3 and greater than −1.5 and dielectricallynegative compounds having a dielectric anisotropy of −1.5 or less.

In a preferred embodiment of the present invention, the liquid-crystalmedium comprises one or more compounds of formula I, preferably selectedfrom the group of the compounds of the formulae I-1 and I-2, preferablyof the formulae I-1 and/or I-2, preferably simultaneously one or morecompounds of formula I-1 and one or more compounds of formula I-2, andoptionally, preferably obligatorily, one or more compounds of formulaI-3, more preferably these compounds of formula I predominantly consist,even more preferably essentially consist and very particularlypreferably completely consist thereof:

in which

-   L1 is H or F, preferably H    and the other parameters have the respective meanings indicated    above for formula I and preferably-   R¹ denotes unfluorinated alkyl having 1 to 7 C atoms or    unfluorinated alkenyl having 2 to 7 C atoms.

The media preferably comprise one or more compounds of formula I-1,which are preferably selected from the group of the compounds of theformulae I-1a to I-1c, preferably of formula I-1c, more preferably thesecompounds of formula I-1 predominantly consist, even more preferablyessentially consist and very particularly preferably completely consistthereof:

in which the parameters have the respective meanings indicated above forformula I-1 and in which preferably

-   R¹¹ denotes alkyl or alkenyl.

The media preferably comprise one or more compounds of formula I-2,which are preferably selected from the group of the compounds of theformulae I-2a to I-2d, preferably of formula I-2d, more preferably thesecompounds of formula I-2 predominantly consist, even more preferablyessentially consist and very particularly preferably completely consistthereof:

in which the parameters have the respective meanings indicated above forformula I-2 and in which preferably

-   R¹ denotes alkyl or alkenyl.

The media preferably comprise one or more compounds of formula I-3,which are preferably selected from the group of the compounds of theformulae I-3a to I-3d, preferably of formula I-3c, more preferably thesecompounds of formula I-2 predominantly consist, even more preferablyessentially consist and very particularly preferably completely consistthereof:

in which the parameters have the respective meanings indicated above forformula I-2 and in which preferably

-   R¹ denotes alkyl or alkenyl.

In an even more preferred embodiment of the present invention, thecompounds of formula I are selected from the group of the compounds I-1aand I-1b, preferably selected from the group of the compounds I-1c andI-1d, more preferably the compounds of formula I predominantly consist,even more preferably essentially consist and very particularlypreferably completely consist thereof:

The media preferably comprise one or more compounds of formula II, whichare preferably selected from the group of the compounds of the formulaeII-1 to II-3, preferably selected from the group of the compounds of theformulae II-1 and II-2, more preferably these compounds of formula IIpredominantly consist, even more preferably essentially consist and veryparticularly preferably completely consist thereof:

in which the parameters have the meanings given under formula II aboveand preferably

-   R² denotes H, unfluorinated alkyl or alkoxy having 1 to 7 C atoms or    unfluorinated alkenyl having 2 to 7 C atoms,    and one of

denotes

-   -   and the other, independently denotes

preferably

-   -   most preferably

and preferably

-   R² denotes C_(n)H_(2n+1) or CH₂=CH—(CH₂)_(z), and-   z denotes 0, 1, 2, 3 or 4, preferably 0 or 2.

The media preferably comprise one or more compounds of formula II-1,which are preferably selected from the group of the compounds of theformulae II-1a to II-1e, preferably selected from the group of thecompounds of the formulae II-1a and II-1b, more preferably of formulaII-1 b, more preferably these compounds of formula II-1 predominantlyconsist, even more preferably essentially consist and very particularlypreferably completely consist thereof:

in which

-   R² has the meaning indicated above and preferably denotes    C_(n)H_(2n+1) or CH₂=CH—(CH₂)_(z), and-   n and m, independently of one another, denote an integer in the    range from 0 to 15, preferably in the range from 1 to 7 and    particularly preferably 1 to 5, and-   z denotes 0, 1, 2, 3 or 4, preferably 0 or 2.

The media preferably comprise one or more compounds of formula II-2,which are preferably selected from the group of the compounds of theformulae II-2a to II-2e, preferably selected from the group of thecompounds of the formulae II-2a and II-2b, more preferablysimultaneously one or more compounds of formula II-2a and one or morecompounds of formula II-2b, more preferably these compounds of formulaII-2 predominantly consist, even more preferably essentially consist andvery particularly preferably completely consist thereof:

in which

-   R² has the meaning indicated above and preferably denotes    C_(n)H_(2n+1) or CH₂=CH—(CH₂)_(z),-   n and m, independently of one another, denote an integer in the    range from 0 to 15, preferably in the range from 1 to 7 and    particularly preferably 1 to 5, and-   z denotes 0, 1, 2, 3 or 4, preferably 0 or 2.

The media preferably comprise one or more compounds of formula II-3,which are preferably selected from the group of the compounds of the offormulae II-3a to II-3e, preferably selected from the group of thecompounds of formulae II-3a and II-3b, more preferably simultaneouslyone or more compounds of formula II-3a and one or more compounds offormula II-3b, more preferably these compounds of formula II-3predominantly consist, even more preferably essentially consist and veryparticularly preferably completely consist thereof:

in which

-   R² has the meaning indicated above and preferably denotes    C_(n)H_(2n+1) or CH₂=CH—(CH₂)_(z),-   n and m, independently of one another, denote an integer in the    range from 0 to 15, preferably in the range from 1 to 7 and    particularly preferably 1 to 5, and-   z denotes 0, 1, 2, 3 or 4, preferably 0 or 2.

The media preferably comprise one or more compounds of formula III,which are preferably selected from the group of the compounds of theformulae III-1 to III-6, more preferably these compounds of the formulaeselected from the group of the compounds of the formulae III-1, III-1,III-2 and III-4, more preferably of formula III-1 and, even morepreferably these compounds of formula III predominantly consist, evenmore preferably essentially consist and very particularly preferablycompletely consist thereof:

in which

-   Z³¹ and Z³² independently of one another denote trans-CH═CH— or    trans-CF=CF—, preferably trans-CH═CH—, and in formula II-6    alternatively one of Z³¹ and Z³² may denote —C≡C— and the other    parameters have the meaning given above under formula III, and    preferably-   R³ denotes H, unfluorinated alkyl or alkoxy having 1 to 7 C atoms or    unfluorinated alkenyl having 2 to 7 C atoms,    and one of

preferably

denotes

preferably

-   -   and the others, independently of one another, denote

preferably

more preferably

and preferably

-   R³ denotes C_(n)H_(2n+1) or CH₂=CH—(CH₂)_(z),-   n and m, independently of one another, denote an integer in the    range from 0 to 15, preferably in the range from 1 to 7 and    particularly preferably 1 to 5, and-   z denotes 0, 1, 2, 3 or 4, preferably 0 or 2.

The media preferably comprise one or more compounds of formula II-1,which are preferably selected from the group of the compounds of theformulae III-1a to III-1d, preferably selected from the group of thecompounds of the formulae III-1a and III-1b, more preferably of formulaIII-1b, and, even more preferably, these compounds of formula III-1predominantly consist, even more preferably essentially consist and veryparticularly preferably completely consist thereof:

in which

-   R³ has the meaning indicated above and preferably denotes    C_(n)H_(2n+1) or CH₂=CH—(CH₂)_(z),-   n and m, independently of one another, denote an integer in the    range from 0 to 15, preferably in the range from 1 to 7 and    particularly preferably 1 to 5, and-   z denotes 0, 1, 2, 3 or 4, preferably 0 or 2.

The media preferably comprise one or more compounds of formula III-2,which are preferably compounds of formula III-2a:

in which

-   R³ has the meaning indicated above and preferably denotes    C_(n)H_(2n+1) or CH₂=CH—(CH₂)_(z),-   n and m, independently of one another, denote an integer in the    range from 0 to 15, preferably in the range from 1 to 7 and    particularly preferably 1 to 5, and-   z denotes 0, 1, 2, 3 or 4, preferably 0 or 2.

The media preferably comprise one or more compounds of formula III-3and/or one or more compounds of formula III-4.

The media preferably comprise one or more compounds of formula III-5,which are preferably compounds of formula III-5a:

-   R³ has the meaning indicated above for formula III-5 and preferably    denotes C_(n)H_(2n+1), in which-   n denotes an integer in the range from 0 to 7, preferably in the    range from 1 to 5, and-   X²² denotes —F, —Cl, —OCF₃, —CN or —NCS, particularly preferably    —NCS.

Further preferred compounds of formula III are the compounds of thefollowing formulae:

in which

-   n denotes an integer in the range from 0 to 7, preferably in the    range from 1 to 5.

Suitable and preferred polymerisation methods are, for example,thermally induced polymerization or photo polymerisation, preferablyphotopolymerisation, in particular UV photopolymerisation. One or moreinitiators can optionally also be added here. Suitable conditions forthe polymerisation and suitable types and amounts of initiators areknown to the person skilled in the art and are described in theliterature. Suitable for free-radical polymerisation are, for example,and preferably, the commercially available photoinitiators Irgacure®184,Irgacure®369, Irgacure®651, Irgacure®784 (preferably), Irgacure®819(preferably), Irgacure®907 or Irgacure®1300 (all from BASF) orDarocure®1173 (from Ciba AG). If an initiator is employed, itsproportion is preferably 0.001% to 5% by weight, particularly preferably0.001% to 1% by weight.

The polymerisable compounds according to the invention are also suitablefor polymerisation without an initiator, which is accompanied byconsiderable advantages, such as, for example, lower material costs andin particular less contamination of the LC medium by possible residualamounts of the initiator or degradation products thereof. Thepolymerisation can thus also be carried out without the addition of aninitiator. In a preferred embodiment, the LC medium thus comprises nopolymerisation initiator.

The polymerisable component or the LC medium may also comprise one ormore stabilisers in order to prevent undesired spontaneouspolymerisation of the RMs, for example during storage or transport.Suitable types and amounts of stabilisers are known to the personskilled in the art and are described in the literature. Particularlysuitable are, for example, the commercially available stabilisers fromthe Irganox® series (from Ciba AG), such as, for example, Irganox® 1076.If stabilisers are employed, their proportion, based on the total amountof the mixture of LS including the RMs or the polymerisable component,is preferably in the range from 10 ppm to 10,000 ppm, particularlypreferably in the range from 50 ppm to 2,000 ppm, most preferably 0.2%or about 0.2%.

The mixtures are characterised as described below before thepolymerisation. The reactive components are then polymerised byirradiation once (180 s), and the resultant media are re-characterised.

The polymerisation of the media preferably is carried out by irradiationwith a UV lamp (e.g. Dymax, Bluewave 200, 365 nm interference filter)having an effective power of about 3.0 mW/cm² for 180 seconds. Thepolymerisation is carried out directly in the test cell/antenna device.To minimize UV induced host degradation a suitable long pass filter isbeneficially applied, for example Schott GG395 or GG410.

The polymerisation is carried out at room temperature.

The entire irradiation time which results in maximum stabilisation istypically 180 s at the irradiation power indicated. Furtherpolymerisations can be carried out in accordance with an optimisedirradiation/temperature programme.

The total concentration of the polymerisable compounds in the mediumprior to polymerisation preferably is in the range form 1% to 20%, morepreferably from 2% to 15% and, most preferably from 2% to 10%.

In a preferred embodiment of the present invention, the medium comprisesone or more dielectrically positive compounds of formula I-1 having adielectric anisotropy of greater than 3.

The medium preferably comprises one or more dielectrically neutralcompounds of formula I-2 having a dielectric anisotropy in the rangefrom more than −1.5 to 3.

In a preferred embodiment of the present invention, the medium comprisesone or more compounds of formula II.

In a further preferred embodiment of the present invention, the mediumcomprises one or more compounds of formula III.

The liquid-crystalline media, preferably or better the nematic componentof the liquid ctrystalline media used in accordance with the presentinvention preferably comprise 10% or less, preferably 5% or less,particularly preferably 2% or less, very particularly preferably 1% orless, and in particular absolutely no compound having only two or fewerfive- and/or six-membered rings.

The definitions of the abbreviations (acronyms) are likewise indicatedbelow in Table D or are evident from Tables A to C.

The liquid-crystalline media in accordance with the present inventionpreferably comprise, more preferably predominantly consist of, even morepreferably essentially consist of and very preferably completely consistof compounds selected from the group of the compounds of the formulae Ito V, preferably I to IV and very preferably I to III and/or V.

In a preferred embodiment of the present inventin the liquid-crystallinemedia predominantly consist of, more preferably essentially consist of,and, most preferably completely consist of isothiocyanate compounds,preferably selected from the group of the compounds of the formulae I toIII.

In this application, “comprise” in connection with compositions meansthat the entity in question, i.e. the medium or the component, comprisesthe component or components or compound or compounds indicated,preferably in a total concentration of 10% or more and very preferably20% or more.

In this connection, “predominantly consist of” means that the entity inquestion comprises 55% or more, preferably 60% or more and verypreferably 70% or more of the component or components or compound orcompounds indicated.

In this connection, “essentially consist of” means that the entity inquestion comprises 80% or more, preferably 90% or more and verypreferably 95% or more of the component or components or compound orcompounds indicated.

In this connection, “completely consist of” means that the entity inquestion comprises 98% or more, preferably 99% or more and verypreferably 100.0% of the component or components or compound orcompounds indicated.

Other mesogenic compounds which are not explicitly mentioned above canoptionally and advantageously also be used in the media in accordancewith the present invention. Such compounds are known to the personskilled in the art.

Preferably the total concentration of the compounds of formulae I to IIIin the medium is in the range from 80% or more to 100%, more preferablyin the range from 90% or more to 100% and most preferably in the rangefrom 95% or more to 100%.

The total concentration of the compounds of formula I-3, preferably ofthe formula I-3c, in the media is in the range from 10% to 45% or less,more preferably from 15% or more to 35% or lessmore preferably from 20%or more to 33% or less and, most preferably from 25% or more to 30% orless.

The liquid-crystal media in accordance with the present inventionpreferably have a clearing point of 90° C. or more, more preferably 100°C. or more, still more preferably 120° C. or more, particularlypreferably 150° C. or more and very particularly preferably 170° C. ormore.

The nematic phase of the media in accordance with the inventionpreferably extends at least from 20° C. or less to 90° C. or more,preferably up to 100° C. or more, more preferably at least from 0° C. orless to 120° C. or more, very preferably at least from −10° C. or lessto 140° C. or more and in particular at least from −20° C. or less to150° C. or more.

The Δε of the liquid-crystal medium in accordance with the invention, at1 kHz and 20° C., is preferably 1 or more, more preferably 2 or more andvery preferably 3 or more.

The Δn of the liquid-crystal media in accordance with the presentinvention, at 589 nm (Na^(D)) and 20° C., is preferably in the rangefrom 0.200 or more to 0.90 or less, more preferably in the range from0.250 or more to 0.90 or less, even more preferably in the range from0.300 or more to 0.85 or less and very particularly preferably in therange from 0.350 or more to 0.800 or less.

In a first preferred embodiment of the present application, the Δn ofthe liquid-crystal media in accordance with the present invention ispreferably 0.50 or more, more preferably 0.55 or more.

In accordance with the present invention, the individual compounds offormula I are preferably used in a total concentration of 10% to 70%,more preferably 20% to 60%, even more preferably 30% to 50% and verypreferably 25% to 45% of the mixture as a whole.

The compounds of formula II are preferably used in a total concentrationof 1% to 20%, more preferably 1% to 15%, even more preferably 2% to 15%and very preferably 3% to 10% of the mixture as a whole.

The compounds of formula III are preferably used in a totalconcentration of 1% to 60%, more preferably 5% to 50%, even morepreferably 10% to 45% and very preferably 15% to 40% of the mixture as awhole.

The liquid-crystal media preferably comprise, preferably predominantlyconsist of and very preferably completely consist of in total 50% to100%, more preferably 70% to 100% and very preferably 80% to 100% and inparticular 90% to 100% of the compounds of the formulae I, II, III, IVand V, preferably of the formulae I, III, IV and V, more preferably ofthe formulae I, II, III, IV and/or VI.

In the present application, the expression dielectrically positivedescribes compounds or components where Δε>3.0, dielectrically neutraldescribes those where −1.5≤Δε≤3.0 and dielectrically negative describesthose where Δε<−1.5. Δε is determined at a frequency of 1 kHz and at 20°C. The dielectric anisotropy of the respective compound is determinedfrom the results of a solution of 10% of the respective individualcompound in a nematic host mixture. If the solubility of the respectivecompound in the host mixture is less than 10%, the concentration isreduced to 5%. The capacitances of the test mixtures are determined bothin a cell having homeotropic alignment and in a cell having homogeneousalignment. The cell thickness of both types of cells is approximately 20μm. The voltage applied is a rectangular wave having a frequency of 1kHz and an effective value of typically 0.5 V to 1.0 V, but it is alwaysselected to be below the capacitive threshold of the respective testmixture.

Δε is defined as (ε∥−ε_(⊥)), while ε_(ave.) is (ε∥+2ε_(⊥))/3.

The host mixture used for dielectrically positive compounds is mixtureZLI-4792 and that used for dielectrically neutral and dielectricallynegative compounds is mixture ZLI-3086, both from Merck KGaA, Germany.The absolute values of the dielectric constants of the compounds aredetermined from the change in the respective values of the host mixtureon addition of the compounds of interest. The values are extrapolated toa concentration of the compounds of interest of 100%.

Components having a nematic phase at the measurement temperature of 20°C. are measured as such, all others are treated like compounds.

The expression threshold voltage in the present application refers tothe optical threshold and is quoted for 10% relative contrast (V₁₀), andthe expression saturation voltage refers to the optical saturation andis quoted for 90% relative contrast (V₉₀), in both cases unlessexpressly stated otherwise. The capacitive threshold voltage (V₀), alsocalled the Freeder-icks threshold (V_(Fr)), is only used if expresslymentioned.

The parameter ranges indicated in this application all include the limitvalues, unless expressly stated otherwise.

The different upper and lower limit values indicated for various rangesof properties in combination with one another give rise to additionalpreferred ranges.

Throughout this application, the following conditions and definitionsapply, unless expressly stated otherwise. All concentrations are quotedin percent by weight and relate to the respective mixture as a whole,all temperatures are quoted in degrees Celsius and all temperaturedifferences are quoted in differential degrees. All physical propertiesare determined in accordance with “Merck Liquid Crystals, PhysicalProperties of Liquid Crystals”, Status November 1997, Merck KGaA,Germany, and are quoted for a temperature of 20° C., unless expresslystated otherwise. The optical anisotropy (Δn) is determined at awavelength of 589.3 nm. The dielectric anisotropy (Δε) is determined ata frequency of 1 kHz. The threshold voltages, as well as all otherelectro-optical properties, are determined using test cells produced atMerck KGaA, Germany. The test cells for the determination of Δε have acell thickness of approximately 20 μm. The electrode is a circular ITOelectrode having an area of 1.13 cm² and a guard ring. The orientationlayers are SE-1211 from Nissan Chemicals, Japan, for homeotropicorientation (ε∥) and polyimide AL-1054 from Japan Synthetic Rubber,Japan, for homogeneous orientation (ε_(⊥)). The capacitances aredetermined using a Solatron 1260 frequency response analyser using asine wave with a voltage of 0.3 V_(rms). The light used in theelectro-optical measurements is white light. A set-up using acommercially available DMS instrument from Autronic-Melchers, Germany,is used here. The characteristic voltages have been determined underperpendicular observation. The threshold (V₁₀), mid-grey (V₅₀) andsaturation (V₉₀) voltages have been determined for 10%, 50% and 90%relative contrast, respectively.

The liquid-crystalline media are investigated with respect to theirproperties in the microwave frequency range as described in A.Penirschke, S. Müller, P. Scheele, C. Weil, M. Wittek, C. Hock and R.Jakoby: “Cavity Perturbation Method for Characterization of LiquidCrystals up to 35 GHz”, 34^(th) European Microwave Conference—Amsterdam,pp. 545-548.

Compare in this respect also A. Gaebler, F. Gölden, S. Müller, A.Penirschke and R. Jakoby “Direct Simulation of Material Permittivites .. . ”, 12MTC 2009—International Instrumentation and MeasurementTechnology Conference, Singapore, 2009 (IEEE), pp. 463-467, and DE 102004 029 429 A, in which a measurement method is likewise described indetail.

The liquid crystal is introduced into a polytetrafluoroethylene (PTFE)capillary. The capillary has an internal radius of 180 μm and anexternal radius of 350 μm. The effective length is 2.0 cm. The filledcapillary is introduced into the centre of the cavity with a resonancefrequency of 30 GHz. This cavity has a length of 6.6 mm, a width of 7.1mm and a height of 3.6 mm. The input signal (source) is then applied,and the result of the output signal is recorded using a commercialvector network analyser.

The change in the resonance frequency and the Q factor between themeasurement with the capillary filled with the liquid crystal and themeasurement without the capillary filled with the liquid crystal is usedto deter-mine the dielectric constant and the loss angle at thecorresponding target frequency by means of equations 10 and 11 in A.Penirschke, S. Müller, P. Scheele, C. Weil, M. Wittek, C. Hock and R.Jakoby: “Cavity Perturbation Method for Characterization of LiquidCrystals up to 35 GHz”, 34^(th) European Microwave Conference—Amsterdam,pp. 545-548, as described therein.

The values for the components of the properties perpendicular andparallel to the director of the liquid crystal are obtained by alignmentof the liquid crystal in a magnetic field. To this end, the magneticfield of a permanent magnet is used. The strength of the magnetic fieldis 0.35 tesla. The alignment of the magnets is set correspondingly andthen rotated correspondingly through 90°.

Preferred components are phase shifters, varactors, wireless and radiowave antenna arrays, matching circuit adaptive filters and others.

In the present application, the term compounds is taken to mean both onecompound and a plurality of compounds, unless expressly statedotherwise.

The liquid-crystal media according to the invention preferably havenematic phases of in each case at least from −20° C. to 80° C.,preferably from −30° C. to 85° C. and very particularly preferably from−40° C. to 100° C.

The phase particularly preferably extends to 120° C. or more, preferablyto 140° C. or more and very particularly preferably to 180° C. or more.The expression have a nematic phase here means on the one hand that nosmectic phase and no crystallisation are observed at low temperatures atthe corresponding temperature and on the other hand that no clearingoccurs on heating from the nematic phase. The investigation at lowtemperatures is carried out in a flow viscometer at the correspondingtemperature and checked by storage in test cells having a layerthickness of 5 μm for at least 100 hours. At high temperatures, theclearing point is measured in capillaries by conventional methods.

Furthermore, the liquid-crystal media according to the invention arecharacterised by high optical anisotropy values in the visible range,especially at a wavelength of 589.0 nm (i.e. at the Na“D” line). Thebirefringence at 589 nm is preferably 0.20 or more, particularlypreferably 0.25 or more, particularly preferably 0.30 or more,particularly preferably 0.40 or more and very particularly preferably0.45 or more. In addition, the birefringence is preferably 0.80 or less.

The liquid crystals employed preferably have a positive dielectricanisotropy. This is preferably 2 or more, preferably 4 or more,particularly preferably 6 or more and very particularly preferably 10 ormore.

Furthermore, the liquid-crystal media according to the invention arecharacterised by high anisotropy values in the microwave range. Thebirefringence at about 8.3 GHz is, for example, preferably 0.14 or more,particularly preferably 0.15 or more, particularly preferably 0.20 ormore, particularly preferably 0.25 or more and very particularlypreferably 0.30 or more. In addition, the birefringence is preferably0.80 or less.

The dielectric anisotropy in the microwave range is defined as

Δε_(r)≡(ε_(r,∥)−ε_(r,⊥)).

The tuneability (τ) is defined as

τ≡(Δε_(r)/ε_(r,∥)).

The material quality (η) is defined as

η≡(τ/tan δ_(εr,max)), where

the maximum dielectric loss is

tan δ_(εr,max.)≡max.{tan δ_(ε,r,⊥,);tan δ_(ε,r,∥)}.

The material quality (η) of the preferred liquid-crystal materials is 6or more, preferably 8 or more, preferably 10 or more, preferably 15 ormore, preferably 17 or more, preferably 20 or more, particularlypreferably 25 or more and very particularly preferably 30 or more.

In the corresponding components, the preferred liquid-crystal materialshave phase shifter qualities of 15°/dB or more, preferably 20°/dB ormore, preferably 30°/dB or more, preferably 40°/dB or more, preferably50°/dB or more, particularly preferably 80°/dB or more and veryparticularly preferably 100°/dB or more.

In some embodiments, however, liquid crystals having a negative value ofthe dielectric anisotropy can also advantageously be used.

The concentration of the chiral dopant, respectively the totalconcentration of the chiral dopants in the LC medium are preferably inthe range from 0.001% or more to 20% or less, preferably from 0.05% ormore to 5% or less, more preferably from 0.1% or more to 1% or less,and, most preferably from 0.2% or more to 0.8% or less. These preferredconcnetratin ranges apply in particular to the chiral dopant S-2011,respectively to its enantiomeric form R-2011 (both from Merck KGaA) amndfor chiral dopants havein the same or a similar HTP. For Chiral dopantshaving either a higher or a lower absolute value of the HTP compared toS-2011 these preferred concentrations have to be decreased, respectivelyincreased proportionally according to the ratio of their HTP valuesrelatively to that of S-2011.

The liquid crystals employed are either individual substances ormixtures. They preferably have a nematic phase.

The concentration of the chiral dopant, respectively the totalconcentration of the chiral dopants in the LC medium are preferably inthe range from 0.05% or more to 5% or less, more preferably from 0.1% ormore to 1% or less, and, most preferably from 0.2% or more to 0.8% orless. These preferred concnetratin ranges apply in particular to thechiral dopant S-2011, respectively to its enantiomeric form R-2011 (bothfrom Merck KGaA) amnd for chiral dopants havein the same or a similarHTP. For Chiral dopants having either a higher or a lower absolute valueof the HTP compared to S-2011 these preferred concentrations have to bedecreased, respectively increased proportionally according to the ratioof their HTP values relatively to that of S-2011.

The term “alkyl” preferably encompasses straight-chain and branchedalkyl groups having 1 to 15 carbon atoms, in particular thestraight-chain groups methyl, ethyl, propyl, butyl, pentyl, hexyl andheptyl. Groups having 2 to 10 carbon atoms are generally preferred.

The term “alkenyl” preferably encompasses straight-chain and branchedalkenyl groups having 2 to 15 carbon atoms, in particular thestraight-chain groups. Particularly preferred alkenyl groups are C₂- toC₇-1E-alkenyl, C₄- to C₇-3E-alkenyl, C₅- to C₇-4-alkenyl, C₆- toC₇-5-alkenyl and C₇-6-alkenyl, in particular C₂- to C₇-1E-alkenyl, C₄-to C₇-3E-alkenyl and C₅- to C₇-4-alkenyl. Examples of further preferredalkenyl groups are vinyl, 1E-propenyl, 1E-butenyl, 1E-pentenyl,1E-hexenyl, 1E-heptenyl, 3-butenyl, 3E-pentenyl, 3E-hexenyl,3E-heptenyl, 4-pentenyl, 4Z-hexenyl, 4E-hexenyl, 4Z-heptenyl, 5-hexenyl,6-heptenyl and the like. Groups having up to 5 carbon atoms aregenerally preferred.

The term “fluoroalkyl” preferably encompasses straight-chain groupshaving a terminal fluorine, i.e. fluoromethyl, 2-fluoroethyl,3-fluoropropyl, 4-fluorobutyl, 5-fluoropentyl, 6-fluorohexyl and7-fluoroheptyl. However, other positions of the fluorine are notexcluded.

The term “oxaalkyl” or “alkoxyalkyl” preferably encompassesstraight-chain radicals of the formula C_(n)H_(2n+1)—O—(CH₂)_(m), inwhich n and m each, independently of one another, denote 1 to 10.Preferably, n is 1 and m is 1 to 6.

Compounds containing a vinyl end group and compounds containing a methylend group have low rotational viscosity.

In the present application, both high-frequency technology andhyper-frequency technology denote applications having frequencies in therange from 1 MHz to 1 THz, preferably from 1 GHz to 500 GHz, morepreferably 2 GHz to 300 GHz, particularly preferably from about 5 GHz to150 GHz.

The liquid-crystal media in accordance with the present invention maycomprise further additives and chiral dopants in the usualconcentrations. The total concentration of these further constituents isin the range from 0% to 10%, preferably 0.1% to 6%, based on the mixtureas a whole. The concentrations of the individual compounds used are eachpreferably in the range from 0.1% to 3%. The concentration of these andsimilar additives is not taken into consideration when quoting thevalues and concentration ranges of the liquid-crystal components andliquid-crystal compounds of the liquid-crystal media in thisapplication.

Preferably the media according to the present invention comprise one ormore chiral compounds as chiral dopants in order to adjust theircholesteric pitch. Their total concentration in the media according tothe instant invention is preferably in the range 0.1% to 15%, morepreferably from 1% to 10% and most preferably from 2% to 6%.

The liquid-crystal media in accordance with the present invention maycomprise further additives and chiral dopants in the usualconcentrations. The total concentration of these further constituents isin the range from 0% to 10%, preferably 0.1% to 6%, based on the mixtureas a whole. The concentrations of the individual compounds used are eachpreferably in the range from 0.1% to 3%. The concentration of these andsimilar additives is not taken into consideration when quoting thevalues and concentration ranges of the liquid-crystal components andliquid-crystal compounds of the liquid-crystal media in thisapplication.

Preferably the media according to the present invention comprise one ormore chiral compounds as chiral dopants in order to adjust theircholesteric pitch. Their total concentration in the media according tothe instant invention is preferably in the range 0.1% to 15%, morepreferably from 1% to 10% and most preferably from 2% to 6%.

Optionally the media according to the present invention may comprisefurther liquid crystal compounds in order to adjust the physicalproperties. Such compounds are known to the expert. Their concentrationin the media according to the instant invention is preferably 0% to 30%,more preferably 0.1% to 20% and most preferably 1% to 15%.

The response times are given as rise time (τ_(on)) for the time for thechange of the relative tuning, respectively of the relative contrast forthe electo-optiocal response, from 0% to 90% (t₉₀−t₀), i.e. includingthe delay time (t₁₀−t₀), as decay time (T_(off)) for the time for thechange of the relative tuning, respectively of the relative contrast fortre electo-optiocal response, from 100% back to 10% (t₁₀₀−t₁₀) and asthe total response time (τ_(total))=τ_(on)+τ_(off)), respectively.

The liquid-crystal media according to the invention consist of aplurality of compounds, preferably 3 to 30, more preferably 4 to 20 andvery preferably 4 to 16 compounds. These compounds are mixed in aconventional manner. In general, the desired amount of the compound usedin the smaller amount is dissolved in the compound used in the largeramount. If the temperature is above the clearing point of the compoundused in the higher concentration, it is particularly easy to observecompletion of the dissolution process. It is, however, also possible toprepare the media in other conventional ways, for example usingso-called pre-mixes, which can be, for example, homologous or eutecticmixtures of compounds, or using so-called “multibottle” systems, theconstituents of which are themselves ready-to-use mixtures.

All temperatures, such as, for example, the melting point T(C,N) orT(C,S), the transition from the smectic (S) to the nematic (N) phaseT(S,N) and the clearing point T(N,I) of the liquid crystals, are quotedin degrees Celsius. All temperature differences are quoted indifferential degrees.

In the present invention and especially in the following examples, thestructures of the mesogenic compounds are indicated by means ofabbreviations, also referred to as acronyms. In these acronyms, thechemical formulae are abbreviated as follows using Tables A to C below.All groups C_(n)H_(2n+1), C_(m)H_(2m+1) and C_(l)H_(2l−1) orC_(n)H_(2n−1), C_(m)H_(2m−1) and C_(l)H_(2l−1) denote straight-chainalkyl or alkenyl, preferably 1-E-alkenyl, respectively, in each casehaving n, m or I C atoms. Table A lists the codes used for the ringelements of the core structures of the compounds, while Table B showsthe linking groups. Table C gives the meanings of the codes for theleft-hand or right-hand end groups. Table D shows illustrativestructures of compounds with their respective abbreviations.

TABLE A Ring elements

C

D

DI

A

AI

P

G

GI

U

UI

Y

M

MI

N

NI

Np

N3f

N3fI

tH

tHI

tH2f

tH2fI

dH

K

KI

L

LI

F

FI

P(o)

PI(o)

P(i3)

PI(ic3)

P(t4)

PI(t4)

P(c3)

PI(c3)

P(c4)

PI(c4)

P(c5)

PI(c5)

P(e5)

PI(e5)

P(c6)

PI(c6)

P(e6)

PI(e6)

GI(o)

G(o)

GI(i3)

G(i3)

GI(t4)

G(t4)

GI(c3)

G(c3)

GI(c4)

G(c4)

GI(c5)

G(c5)

GI(e5)

G(e5)

GI(c6)

G(c6)

GI(e6)

G(e6)

N(1,4)

TABLE B Linking groups E —CH₂CH₂— V —CH═CH— X —CF═CH— XI —CH═CF— B—CF═CF— T —C≡C— W —CF₂CF₂— Z —CO—O— ZI —O—CO— O —CH₂—O— OI —O—CH₂— Q—CF₂—O— QI —O—CF₂—

TABLE C End groups Left-hand side Right-hand side Used alone -n-C_(n)H_(2n+1)— -n —C_(n)H_(2n+1) -nO- C_(n)H_(2n+1)—O— -nO—O—C_(n)H_(2n+1) -V- CH₂═CH— -V —CH═CH₂ -nV- C_(n)H_(2n+1)—CH═CH— -nV—C_(n)H_(2n)—CH═CH₂ -Vn- CH₂═CH—C_(n)H_(2n+1)— -Vn —CH═CH—C_(n)H_(2n+1)-nVm- C_(n)H_(2n+1)—CH═CH—C_(m)H_(2m)— -nVm—C_(n)H_(2n)—CH═CH—C_(m)H_(2m+1) -N- N≡C— -N —C≡N -S- S═C═N— -S —N═C═S-F- F— -F —F -CL- Cl— -CL —Cl -M- CFH₂— -M —CFH₂ -D- CF₂H— -D —CF₂H -T-CF₃— -T —CF₃ -MO- CFH₂O— -OM —OCFH₂ -DO- CF₂HO— -OD —OCF₂H -TO- CF₃O—-OT —OCF₃ -OXF- CF₂═CH—O— -OXF —O—CH═CF₂ -A- H—C≡C— -A —C≡C—H -nA-C_(n)H_(2n+1)—C≡C— -An —C≡C—C_(n)H_(2n+1) -NA- N≡C—C≡C— -AN —C≡C—C≡NUsed in combination with others - . . . A . . . - —C≡C— - . . . A . . .—C≡C— - . . . V . . . - CH═CH— - . . . V . . . —CH═CH— - . . . Z . . . -—CO—O— - . . . Z . . . —CO—O— - . . . ZI . . . - —O—CO— - . . . ZI . . .—O—CO— - . . . K . . . - —CO— - . . . K . . . —CO— - . . . W . . . -—CF═CF— - . . . W . . . —CF═CF—in which n and m each denote integers, and the three dots “ . . . ” areplace-holders for other abbreviations from this table.

The following table shows illustrative structures together with theirrespective abbreviations. These are shown in order to illustrate themeaning of the rules for the abbreviations. They furthermore representcompounds which are preferably used.

TABLE D Illustrative structures The following illustrative structuresare compounds, which are particularly preferably employed, having aterminal —NSC group:

The following illustrative structures are compounds, which arepreferably additionally used in the media:

The following illustrative structures are auxiliary compounds, which areoptionally employed, having three 6-membered rings:

The following illustrative structures are auxiliary compounds, which areoptionally employed, having four 6-membered rings:

Illustrative structures of dielectrically neutral compounds which mayadditionally be employed:

Illustrative structures of further compounds which may additionally beemployed:

The following table, Table E, shows illustrative compounds which can beused as stabiliser in the mesogenic media in accordance with the presentinvention. The total concentration of these and similar compounds in themedia is preferably 5% or less.

TABLE E

In a preferred embodiment of the present invention, the mesogenic mediacomprise one or more compounds selected from the group of the compoundsfrom Table E.

The following table, Table F, shows illustrative compounds which canpreferably be used as chiral dopants in the mesogenic media inaccordance with the present invention.

TABLE F

C 15

CB 15

CM 21

CM 44

CM 45

CM 47

CC

CN

R/S-811

R/S-1011

R/S-2011

R/S-3011

R/S-4011

R/S-5011

In a preferred embodiment of the present invention, the mesogenic mediacomprise one or more compounds selected from the group of the compoundsfrom Table F.

The mesogenic media in accordance with the present applicationpreferably comprise two or more, preferably four or more, compoundsselected from the group consisting of the compounds from the abovetables.

The liquid-crystal media in accordance with the present inventionpreferably comprise

-   -   seven or more, preferably eight or more, compounds, preferably        compounds having three or more, preferably four or more,        different formulae, selected from the group of the compounds        from Table D.

EXAMPLES

The following examples illustrate the present invention without limitingit in any way.

However, it is clear to the person skilled in the art from the physicalproperties what properties can be achieved and in what ranges they canbe modified. In particular, the combination of the various propertieswhich can preferably be achieved is thus well defined for the personskilled in the art.

Examples 1 to 17 and Comparative Example Comparative Example

A liquid-crystal mixture C-1 having the composition and properties asindicated in the following table is prepared and characterized withrespect to its general physical properties and its applicability inmicrowave

Composition Compound Conc./ No. Abbreviation mass-% 1 PPTUI-3-2 20.0 2PPTUI-3-4 36.0 3 GGP-3-CL 10.0 4 GGP-5-CL 20.0 5 CPGP-5-2 7.0 6 CPGP-5-37.0 Σ 100.0 Physical Properties T(N, I)/° C. = 173 Δn(20° C., 589.3 nm)= 0.335 Δε(20° C., 1 kHz) = 4.6 γ₁ (20° C.)/mPa · s = 746 tan δ_(εr,⊥)(20° C., 19 GHz) = 0.0143 tan δ_(εr,||) (20° C., 19 GHz) = 0.0038 τ (20°C., 19 GHz) = 0.252 η (20° C., 19 GHz) = 17.6

This mixture is suitable for applications in the microwave range, inparticular for phase shifters or LC based antenna elements in the microwave (MW) region, however its response times are only moderate and notsufficient for more demanding applications.

Example 1

A liquid-crystal mixture C-1 having the composition and properties asindicated in the following table is prepared and characterized withrespect to its general physical properties and its applicability inmicrowave components at 19 GHz.

Composition Compound No Abbreviation Conc./mass-% 1 PU-3-S 10.0 2PTU-3-S 10.0 3 PTU-5-S 10.0 4 CGU-2-S 20.0 5 CGU-4-S 20.0 6 PGU-3-S 16.07 PPTU-4-S 7.0 8 PPTU-5-S 7.0 Σ 100.0 Physical Properties T (N, I)/° C.= 123 n_(o) (20° C., 589.3 nm) = t.b.d. Δn (20° C., 589.3 nm) = t.b.d.ε_(∥) (20° C., 1 kHz) = 26.9 Δε (20° C., 1 kHz) = 4.7 γ₁ (20° C.)/mPa ·s = 287 k₁ (20° C.)/pN = 14.0 k₃/k₁ (20° C.) = 1.39 V₀ (20° C.)/V = 0.84ε_(r, ⊥) (20° C., 19 GHz) = 2.36 ε_(r, ∥) (20° C., 19 GHz) = 3.42 tanδ_(ε r, ⊥) (20° C., 19 GHz) = 0.0116 tan δ_(ε r, ∥) (20° C., 19 GHz) =0.0066 τ (20° C., 19 GHz) = 0.310 η (20° C., 19 GHz) = 26.7 Remarks:t.b.d.: to be determined

This mixture is suitable for applications in the microwave range, inparticular for phase shifters or LC based antenna elements in the microwave (MW) region. In comparison to the comparative examplethis mixtureclearly exhibits superior response times.

Examples 1.1 and 1.2

The mixture C-1 is divided into three parts. To each one of two thesetwo parts a certain concentration of the chiral dopant S-1011 as shownin table F above, having a negative value of the HTP, is added.

To one each of these two parts alternatively 0.20% of S-1011 and 0.40%of S-1011 are added, respectively.

The two resultant mixtures are called M-1.1 and M-1.2. These twomixtures each are filled into test cells with antiparallel rubbed glassubstrates covered by PI A13046. The test cells have a cell gap of 50μm.

TABLE 1 Compositions of the mixtures investigated Material C-1 S-1011Example Mixture Composition Number Concentration/mass-% C-1 100.00 0.001.1 99.80 0.20 1.2 99.60 0.40

TABLE 2 Physical Properties (at 20° C.) of the mixtures investigatedMixture C-1 M-1.1 M-1.2 Property Value T (N, I)/° C. t.b.d. t.b.d.t.b.d. Δn (20° C., 589.3 nm) t.b.d. t.b.d. t.b.d. Δε (20° C., 1 kHz)t.b.d. t.b.d. t.b.d. γ₁ (20° C.)/mPa · s t.b.d. t.b.d. t.b.d. V₀/Vt.b.d. t.b.d. t.b.d. Remarks: t.b.d.: to be determined, V₀ in 91 μm testcell, described above.

TABLE 3 Microwave characteristics and response times (at 20° C.) of themixtures investigated Mixture C-1 M-1.1 M-1.2 Property Value tanδ_(ε r, ⊥) (20° C., 19 GHz) t.b.d. t.b.d. t.b.d. tan δ_(ε r, ∥) (20° C.,19 GHz) t.b.d. t.b.d. t.b.d. τ (20° C., 19 GHz) t.b.d. t.b.d. t.b.d. η(20° C., 19 GHz) t.b.d. t.b.d. t.b.d. τ_(on)/s t.b.d. t.b.d. t.b.d.τ_(off)/s 4.1 1.0 0.25 τ_(sum)/s t.b.d. t.b.d. t.b.d. Remarks: t.b.d.:to be determined.

These two mixtures are very highly suitable for applications in themicrowave range, in particular for phase shifters or LC based antennaelements in the micro wave (MW) region. Additionally in comparison tothe Examples 1.1 and 1.2 these mixtures clearly exhibit superior, i.e.significanly samller, response times. Mixture M-1.2, which iscomprisuing the higher concentration of the chiral compound compared toM-1.1, has an even more strongly improved response behaviour.

The switching times are determined from the electro-optical response intest cells with antiparallel rubbed polyimide (PI) orientation layers ontop of ITO electrodes on glass substrates. These cells have a cell gapof 91 μm. They are investigated in an optical setup as follows. A testcell is mounted on a temperature-controlled chuck (20° C.) with anantireflective layer between the test cell and the chuck. The test cellis illuminated by a white LED light source from an angle of 45°. Nopolarizers are used on the test cell.

A rectangular bipolar bias voltage with a frequency of 1 kHz and anamplitude of 100 V is applied to the LC layer in the test cell. Thisbias voltage is subsequently switched on and off. The test cell isplaced in the light path of a microscope (objective lens 5×) and canthus be can be visually observed and inspected. During the switchingoperation, the brightness of the cell observed through the microscopechanges following the changes in the bias voltage. A photodiodeinstalled within the light path of the microscope is used to record thechange of the brightness of the LC layer investigated in the test cellvia an external photodiode amplifier (Thorlabs PDA200C).

The response times for switching on and for switching off are determinedfor the time required to change the relative intensity of reflectionfrom10% to 90% and vice versa, respectively.

τ_(on) ≡t(10%)−t(90%)

τ_(off) ≡t(90%)−t(10%)

Example 2

A liquid-crystal mixture M-2 having the composition and properties asindicated in the following table is prepared and characterized withrespect to its general physical properties and its applicability inmicrowave components at 19 GHz.

Composition Compound No Abbreviation Conc./mass-% 1 PU-3-S 16.0 2PVG-4-S 13.0 3 PVG-5-S 13.0 4 PTU-3-S 7.0 5 PTU-5-S 7.0 6 PGU-3-S 24.0 7PPTU-4-S 10.0 8 PPTU-5-S 10.0 Σ 100.0 Physical Properties T (N, I)/° C.= 100 n_(o) (20° C., 589.3 nm) = t.b.d. Δn (20° C., 589.3 nm) = t.b.d.ε_(∥) (20° C., 1 kHz) = 28.2 Δε (20° C., 1 kHz) = 5.0 γ₁ (20° C.)/mPa ·s = 245 tan δ_(ε r, ⊥) (20° C., 19 GHz) = t.b.d. tan δ_(ε r, ∥) (20° C.,19 GHz) = t.b.d. τ (20° C., 19 GHz) = t.b.d. η (20° C., 19 GHz) = t.b.d.Remark: t.b.d.: to be determined.k₁₁=15.8 pN; k₃₃=15.1 V; V₁₀=0.87 V

This mixture is suitable for applications in the microwave range, inparticular for phase shifters or LC based antenna elements in the microwave (MW) region. In comparison to the Comparison Example 1 this mixtureclearly exhibits superior response times.

Example 3

A liquid-crystal mixture M-3 having the composition and properties asindicated in the following table is prepared and characterized withrespect to its general physical properties and its applicability inmicrowave components at 19 GHz.

Composition Compound No Abbreviation Conc./mass-% 1 PU-3-S 18.0 2PVG-4-S 13.0 3 PVG-5-S 13.0 4 PTU-3-S 8.0 5 PTU-5-S 8.0 6 PGU-3-S 20.0 7PPTU-4-S 10.0 8 PPTU-5-S 10.0 Σ 100.0 Physical Properties T (N, I)/° C.= 93 n_(o) (20° C., 589.3 nm) = t.b.d. Δn (20° C., 589.3 nm) = t.b.d.ε_(∥) (20° C., 1 kHz) = 27.7 Δε (20° C., 1 kHz) = 5.0 γ₁ (20° C.)/mPa ·s = 225 tan δ_(ε r, ⊥) (20° C., 19 GHz) = t.b.d. tan δ_(ε r, ∥) (20° C.,19 GHz) = t.b.d. τ (20° C., 19 GHz) = t.b.d. η (20° C., 19 GHz) = t.b.d.Remark: t.b.d.: to be determined.k₁₁=15.0 pN; k₃₃=15.4 V; V₁₀=0.86 V

This mixture is suitable for applications in the microwave range, inparticular for phase shifters or LC based antenna elements in the microwave (MW) region. In comparison to the comparative example this mixtureclearly exhibits superior response times.

TABLE 5 Comparison of the properties at 19 GHz and 20° C. Example Liquidcrystal Δε_(r⊥) δ_(ε r, ⊥) η 1 M-1 0.56 0.013 14.5 Comparison 5CB 0.0264.3

Example 4

A liquid-crystal mixture M-4 having the composition and properties asindicated in the following table is prepared.

Composition Compound No Abbreviation Conc./mass-% 1 CP-3-CL 10.0 2PVG-4-S 11.0 3 PVG-5-S 11.0 4 PTU-3-S 10.0 5 PTU-5-S 10.0 6 CPU-3-S 14.07 PGU-3-S 20.0 8 PPTU-4-S 7.0 9 PPTU-5-S 7.0 Σ 100.0 Physical PropertiesT (N, I)/° C. = 72 n_(e) (20° C., 589.3 nm) = t.b.d. Δn (20° C., 589.3nm) = t.b.d. ε_(∥) (20° C., 1 kHz) = 24.5 Δε (20° C., 1 kHz) = 5.1 k₁₁(20° C.)/pN = 11.3 k₃₃ (20° C.)/pN = 13.2 V₀ (20° C.)/V = 0.81 γ₁ (20°C.)/mPa · s = 162 tan δ_(ε r, max) (20° C., 19 GHz) = t.b.d. τ (20° C.,19 GHz) = t.b.d. η (20° C., 19 GHz) = t.b.d. Remark: t.b.d.: to bedetermined.

This mixture is very highly suitable for applications in the microwaverange, in particular for phase shifters or LC based antenna elements inthe MW region.

Example 5

A liquid-crystal mixture M-5 having the composition and properties asindicated in the following table is prepared.

Composition Compound No Abbreviation Conc./mass-% 1 PVG-3-S 6.0 2PVG-4-S 16.0 3 PVG-5-S 6.0 4 PTG-3-S 10.0 5 PTG-5-S 10.0 6 PTU-3-S 8.0 7PGU-3-S 8.0 8 PPTU-4-S 16.0 9 PPTU-5-S 16.0 Σ 100.0 Physical PropertiesT (N, I)/° C. = 112 n_(o) (20° C., 589.3 nm) = 1.5454 Δn (20° C., 589.3nm) = t.b.d. ε_(∥) (20° C., 1 kHz) = 25.7 Δε (20° C., 1 kHz) = 4.4 γ₁(20° C.)/mPa · s = 270 tan δ_(ε r, ⊥) (20° C., 19 GHz) = 0.0143 tanδ_(ε r, ∥) (20° C., 19 GHz) = 0.0038 τ (20° C., 19 GHz) = 0.252 η (20°C., 19 GHz) = 17.6 Remark: t.b.d.: to be determined.

This mixture is very highly suitable for applications in the microwaverange, in particular for phase shifters or LC based antenna elements inthe MW region.

Example 6

A liquid-crystal mixture M-6 having the composition and properties asindicated in the following table is prepared.

Composition Compound No Abbreviation Conc./mass-% 1 CP-1V-O1 10.0 2PVG-4-S 11.0 3 PVG-5-S 11.0 4 PTU-3-S 10.0 5 PTU-5-S 10.0 6 CPU-3-S 14.07 PGU-3-S 20.0 8 PPTU-4-S 7.0 9 PPTU-5-S 7.0 Σ 100.0 Physical PropertiesT (N, I)/° C. = 75.5 n_(e) (20° C., 589.3 nm) = t.b.d. Δn (20° C., 589.3nm) = t.b.d. ε_(∥) (20° C., 1 kHz) = 24.2 Δε (20° C., 1 kHz) = 5.1 k₁₁(20° C.)/pN 11.7 k₃₃ (20° C.)/pN 13.6 V₀ (20° C.)/V 0.83 γ₁ (20° C.)/mPa· s = 178 tan δ_(εr, max) (20° C., 19 GHz) = τ (20° C., 19 GHz) = η (20°C., 19 GHz) = Remark: t.b.d.: to be determined.

This mixture is very highly suitable for applications in the microwaverange, in particular for phase shifters or LC based antenna elements inthe MW region.

Example 7

A liquid-crystal mixture M-7 having the composition and properties asindicated in the following table is prepared.

Composition Compound No Abbreviation Conc./mass-% 1 GGP-3-S 12.0 2PGG-3-S 8.0 3 PGU-3-S 12.0 4 PVG-3-S 6.0 5 PVG-4-S 16.0 6 PTG-3-S 10.0 7PTG-5-S 18.0 8 PTU-3-S 10.0 9 PPTU-4-S 6.0 Σ 100.0 Physical Properties T(N, I)/° C. = 98 n_(e) (20° C., 589.3 nm) = t.b.d. Δn (20° C., 589.3 nm)= t.b.d. ε_(∥) (20° C., 1 kHz) = 26.7 Δε (20° C., 1 kHz) = t.b.d. k₁₁(20° C.)/pN 17.7 k₃₃ (20° C.)/pN 15.7 V₀ (20° C.)/V 0.96 γ₁ (20° C.)/mPa· s = 698 tan δ_(ε r, max) (20° C., 19 GHz) = 0.0189 τ (20° C., 19 GHz)= 0.336 η (20° C., 19 GHz) = 17.9 Remark: t.b.d.: to be determined.

This mixture is very highly suitable for applications in the microwaverange, in particular for phase shifters or LC based antenna elements inthe MW region.

Examples 8 to 12

To the liquid crystalline medium M-7 of Example 7 alternatively acertain concentration of a further single compound one each is added andthe resultant mixtures (M-8 to M-12) are investigated for their generalphysical properties and for their performance in the microwave regime.

Composition Example Mixture Compound c (Comp.) c (M-4) No. No.Abbreviation /% 7 M-7 None 0.0 100.0 8 M-8 PTPI(c3)TU-4-F 5.0 95.0 9 M-9PTPI(2)WU-6-F 10.0 90.0 10 M-10 PTPI(2)GU-4-F 10.0 90.0 11 M-11PTG(c3)TU-4-F 5.0 95.0 12 M-12 PTN(1, 4)TP-3-F 5.0 95.0

Physical Rroperties I, General I (20° C. except T(N.I)) Example MixtureT (N, I)/ No. No. ° C. Δn ε_(∥) Δε 7 M-7 98 t.b.d. 26.7 21.5 8 M-8 98t.b.d. 26.1 20.9 9 M-9 90 t.b.d. 26.0 21.0 10 M-10 102 t.b.d. 27.0 21.911 M-11 93.9 t.b.d. 27.0 21.8 12 M-12 99.5 t.b.d. 25.9 20.9 Remark:t.b.d.: to be determined.

Physical Rroperties II, General II (20° C.) Example Mixture No. No. γ₁k₁₁/pN k₃₃/pN V₀/V 7 M-7 241 17.7 15.7 0.96 8 M-8 254 15.1 14.6 0.90 9M-9 272 15.8 15.8 0.91 10 M-10 319 16.0 16.9 0.90 11 M-11 257 15.8 15.00.90 12 M-12 273 18.2 15.9 0.99

Physical Rroperties III Microwave I (20° C., 19 GHz) Example Mixture No.No. ε_(r, ⊥) ε_(r, ∥) tan δ_(ε r, ∥) tan δ_(ε r, ⊥) 7 M-7 3.74 2.490.0189 0.0091 8 M-8 3.68 2.48 0.0177 0.0088 9 M-9 3.67 2.49 0.01740.0084 10 M-10 3.68 2.48 0.0170 0.0082 11 M-11 3.70 2.49 0.0180 0.008812 M-12 3.73 2.49 0.0175 0.0085

Physical Rroperties IV, Microwave II (20° C., 19 GHz) Example MixtureNo. No. tan δ_(εr,⊥) τ_(εr) η 7 M-7 0.0189 0.336 17.8 8 M-8 0.0177 0.32618.4 9 M-9 0.0174 0.323 18.6 10 M-10 0.0170 0.327 19.3 11 M-11 0.01800.327 18.1 12 M-12 0.0175 0.332 19.0

These mixtures are very well suitable for applications in the microwaverange, in particular for phase shifters or LC based antenna elements inthe MW region.

The mixtures of examples 7 to 12 are treated and investigated asdescribed under example 1. The resultant mixtures comprising the chiralcompound in the respective concentrations show similarly improvedproperties. They are especially characterized in particular by improvedresponse times.

Example 13

A liquid-crystal mixture M-13 having the composition and properties asindicated in the following table is prepared and characterized withrespect to its general physical properties and its applicability inmicrowave components at 19 GHz.

Composition Compound Conc./ No Abbreviation mass-% 1 PU-3-S 10.0 2PTU-3-S 10.0 3 PTU-5-S 10.0 4 CGU-2-S 10.0 5 CGU-3-S 10.0 6 CGU-4-S 10.07 CGU-5-S 10.0 8 PGU-3-S 16.0 9 PPTU-4-S 7.0 10  PPTU-5-S 7.0 Σ 100.0Physical Properties T(N, I)/° C. = 126.5 n_(o)(20° C., 589.3 nm) =t.b.d. Δn(20° C., 589.3 nm) = t.b.d. ε_(||)(20° C., 1 kHz) = 27.1 Δε(20°C., 1 kHz) = 4.5 γ₁ (20° C.)/mPa · s = 299 k₁ (20° C.)/pN = 14.8 k₃/k₁(20° C.) = 1.43 V₀ (20° C.)/V = 0.86 ε_(r,⊥) (20° C., 19 GHz) = 2.36ε_(r,||) (20° C., 19 GHz) = 3.44 tan δ_(εr,⊥) (20° C., 19 GHz) = 0.0116tan δ_(εr,||) (20° C., 19 GHz) = 0.0064 τ (20° C., 19 GHz) = 0.315 η(20° C., 19 GHz) = 27.2 Remark: t.b.d.: to be determined.

This mixture is suitable for applications in the microwave range, inparticular for phase shifters or LC based antenna elements in the microwave (MW) region. In comparison to the comparative example this mixtureclearly exhibits superior response times.

Example 14

A liquid-crystal mixture M-14 having the composition and properties asindicated in the following table is prepared and characterized withrespect to its general physical properties and its applicability inmicrowave components at 19 GHz.

Composition Compound Conc./ No Abbreviation mass-% 1 PU-3-S 14.0 2PTU-3-S 14.0 3 CGU-2-S 20.0 4 CGU-4-S 20.0 5 PGU-3-S 18.0 6 PPTU-4-S 7.07 PPTU-5-S 7.0 Σ 100.0 Physical Properties T(N, I)/° C. = t.b.d.n_(o)(20° C., 589.3 nm) = t.b.d. Δn(20° C., 589.3 nm) = t.b.d.ε_(||)(20° C., 1 kHz) = t.b.d. Δε(20° C., 1 kHz) = t.b.d. γ₁ (20°C.)/mPa · s = t.b.d. k₁ (20° C.)/pN = t.b.d. k₃/k₁ (20° C.) = t.b.d. V₀(20° C.)/V = t.b.d. ε_(r,⊥) (20° C., 19 GHz) = t.b.d. ε_(r,||) (20° C.,19 GHz) = t.b.d. tan δ_(εr,⊥) (20° C., 19 GHz) = t.b.d. tan δ_(εr,||)(20° C., 19 GHz) = t.b.d. τ (20° C., 19 GHz) = t.b.d. η (20° C., 19 GHz)= t.b.d. Remark: t.b.d.: to be determined.

This mixture is suitable for applications in the microwave range, inparticular for phase shifters or LC based antenna elements in the microwave (MW) region. In comparison to the comparative example this mixtureclearly exhibits superior response times.

Example 15

A liquid-crystal mixture M-15 having the composition and properties asindicated in the following table is prepared and characterized withrespect to its general physical properties and its applicability inmicrowave components at 19 GHz.

Composition Compound Conc./ No Abbreviation mass-% 1 PU-3-S 8.0 2PVG-4-S 8.0 3 PVG-5-S 8.0 4 PTU-3-S 8.0 5 PTU-5-S 8.0 6 CGU-3-S 10.0 7CGU-4-S 10.0 8 CGU-5-S 10.0 9 PGU-3-S 16.0 9 PPTU-4-S 7.0 11  PPTU-5-S7.0 Σ 100.0 Physical Properties T(N, I)/° C. = 121.5 n_(o)(20° C., 589.3nm) = t.b.d. Δn(20° C., 589.3 nm) = t.b.d. ε_(||)(20° C., 1 kHz) = 26.2Δε(20° C., 1 kHz) = 4.6 γ₁ (20° C.)/mPa · s = 298 k₁ (20° C.)/pN = 16.0k₃/k₁ (20° C.) = 1.31 V₀ (20° C.)/V = 0.91 ε_(r,⊥) (20° C., 19 GHz) =2.36 ε_(r,||) (20° C., 19 GHz) = 3.48 tan δ_(εr,⊥) (20° C., 19 GHz) =0.0121 tan δ_(εr,||) (20° C., 19 GHz) = 0.0067 τ (20° C., 19 GHz) =0.321 η (20° C., 19 GHz) = 26.5 Remark: t.b.d.: to be determined.

This mixture is suitable for applications in the microwave range, inparticular for phase shifters or LC based antenna elements in the microwave (MW) region. In comparison to the comparative example this mixtureclearly exhibits superior response times.

Example 16

A liquid-crystal mixture M-16 having the composition and properties asindicated in the following table is prepared and characterized withrespect to its general physical properties and its applicability inmicrowave components at 19 GHz.

Composition Compound Conc./ No Abbreviation mass-% 1 PU-3-S 8.0 2PVG-4-S 8.0 3 PVG-5-S 8.0 4 PTU-3-S 8.0 5 PTU-5-S 8.0 6 CGU-4-S 15.0 7CGU-5-S 15.0 8 PGU-3-S 16.0 9 PPTU-4-S 7.0 10  PPTU-5-S 7.0 Σ 100.0Physical Properties T(N, I)/° C. = 124 n_(o)(20° C., 589.3 nm) = t.b.d.Δn(20° C., 589.3 nm) = t.b.d. ε_(||)(20° C., 1 kHz) = 26.2 Δε(20° C., 1kHz) = 4.6 γ₁ (20° C.)/mPa · s = 311 k₁ (20° C.)/pN = 16.2 k₃/k₁ (20°C.) = 1.28 V₀ (20° C.)/V = 0.91 ε_(r,⊥) (20° C., 19 GHz) = 2.37 ε_(r,||)(20° C., 19 GHz) = 3.48 tan δ_(εr,⊥) (20° C., 19 GHz) = 0.0120 tanδ_(εr,||) (20° C., 19 GHz) = 0.0066 τ (20° C., 19 GHz) = 0.318 η (20°C., 19 GHz) = 26.2 Remark: t.b.d.: to be determined.

This mixture is suitable for applications in the microwave range, inparticular for phase shifters or LC based antenna elements in the microwave (MW) region. In comparison to the comparative example this mixtureclearly exhibits superior response times.

Example 17

A liquid-crystal mixture M-17 having the composition and properties asindicated in the following table is prepared and characterized withrespect to its general physical properties and its applicability inmicrowave components at 19 GHz.

Composition Compound Conc./ No Abbreviation mass-% 1 PU-3-S 10.0 2PTU-3-S 10.0 3 PTU-5-S 10.0 4 CGU-2-S 14.0 5 CGU-3-S 13.0 6 CGU-4-S 13.07 PGU-3-S 16.0 8 PPTU-4-S 7.0 9 PPTU-5-S 7.0 Σ 100.0 Physical PropertiesT(N, I)/° C. = 126.5 n_(o)(20° C., 589.3 nm) = t.b.d. Δn(20° C., 589.3nm) = t.b.d. ε_(||)(20° C., 1 kHz) = 27.4 Δε(20° C., 1 kHz) = 4.6 γ₁(20° C.)/mPa · s = 297 k₁ (20° C.)/ = 14.5 k₃/k₁ (20° C.) = 1.45 V₀ (20°C.)/V = 0.84 ε_(r,⊥) (20° C., 19 GHz) = 2.36 ε_(r,||) (20° C., 19 GHz) =3.44 tan δ_(εr,⊥) (20° C., 19 GHz) = 0.0115 tan δ_(εr,||) (20° C., 19GHz) = 0.0065 τ (20° C., 19 GHz) = 0.313 η (20° C., 19 GHz) = 27.2Remark: t.b.d.: to be determined.

This mixture is suitable for applications in the microwave range, inparticular for phase shifters or LC based antenna elements in the microwave (MW) region. In comparison to the comparative example this mixtureclearly exhibits superior response times.

Example 18

A liquid-crystal mixture M-18 having the composition and properties asindicated in the following table is prepared and characterized withrespect to its general physical properties and its applicability inmicrowave components at 19 GHz.

Composition Compound Conc./ No Abbreviation mass-% 1 PVG-4-S 16.0 2PVG-5-S 16.0 3 PTU-3-S 14.0 4 PTU-5-S 10.0 5 PTG-5-S 14.0 6 PGU-3-S 14.07 PPTU-4-S 15.0 8 PPTU-5-S 15.0 Σ 100.0 Physical Properties T(N, I)/° C.= 115.5 n_(o)(20° C., 589.3 nm) = t.b.d. Δn(20° C., 589.3 nm) = t.b.d.ε_(||)(20° C., 1 kHz) = 27.0 Δε(20° C., 1 kHz) = 4.5 γ₁ (20° C.)/mPa · s= 304 k₁ (20° C.)/pN/ = t.b.d. k₃/k₁ (20° C.) = t.b.d. V₀ (20° C.)/V =1.07 ε_(r,⊥) (20° C., 19 GHz) = t.b.d. ε_(r,||) (20° C., 19 GHz) =t.b.d. tan δ_(εr,⊥) (20° C., 19 GHz) = t.b.d. tan δ_(εr,||) (20° C., 19GHz) = t.b.d. τ (20° C., 19 GHz) = t.b.d. η (20° C., 19 GHz) = t.b.d.Remark: t.b.d.: to be determined.

This mixture is suitable for applications in the microwave range, inparticular for phase shifters or LC based antenna elements in the microwave (MW) region. In comparison to the comparative example this mixtureclearly exhibits superior response times.

Example 19

A liquid-crystal mixture M-19 having the composition and properties asindicated in the following table is prepared and characterized withrespect to its general physical properties and its applicability inmicrowave components at 19 GHz.

Composition Compound Conc./ No Abbreviation mass-% 1 PU-3-S 20.0 2PVG-4-S 16.0 3 PVG-5-S 16.0 4 PGU-3-S 16.0 5 PPTU-4-S 16.0 6 PPTU-5-S16.0 Σ 100.0 Physical Properties T(N, I)/° C. = 116.5 n_(o)(20° C.,589.3 nm) = t.b.d. Δn(20° C., 589.3 nm) = t.b.d. ε_(||)(20° C., 1 kHz) =27.7 Δε(20° C., 1 kHz) = 4.6 γ₁ (20° C.)/mPa · s = 292 k₁ (20° C.)/pN =t.b.d. k₃/k₁ (20° C.) = t.b.d. V₀ (20° C.)/V = 1.05 ε_(r,⊥) (20° C., 19GHz) = t.b.d. ε_(r,||) (20° C., 19 GHz) = t.b.d. tan δ_(εr,⊥) (20° C.,19 GHz) = t.b.d. tan δ_(εr,||) (20° C., 19 GHz) = t.b.d. τ (20° C., 19GHz) = t.b.d. η (20° C., 19 GHz) = t.b.d. Remark: t.b.d.: to bedetermined.

This mixture is suitable for applications in the microwave range, inparticular for phase shifters or LC based antenna elements in the microwave (MW) region. In comparison to the comparative example this mixtureclearly exhibits superior response times.

Example 20

A liquid-crystal mixture M-20 having the composition and properties asindicated in the following table is prepared and characterized withrespect to its general physical properties and its applicability inmicrowave components at 19 GHz.

Composition Compound Conc./ No Abbreviation mass-% 1 PU-3-S 16.0 2PVG-4-S 14.0 3 PVG-5-S 14.0 4 PTU-3-S 8.0 5 PTU-5-S 8.0 6 PGU-3-S 14.0 7PPTU-4-S 10.0 8 PPTU-5-S 10.0 Σ 100.0 Physical Properties T(N, I)/° C. =95 n_(o)(20° C., 589.3 nm) = t.b.d. Δn(20° C., 589.3 nm) = t.b.d.ε_(||)(20° C., 1 kHz) = 27.4 Δε(20° C., 1 kHz) = 5.0 γ₁ (20° C.)/mPa · s= 234 k₁ (20° C.)/pN = 15.6 k₃/k₁ (20° C.) = 1.00 V₀ (20° C.)/V = 0.88ε_(r,⊥) (20° C., 19 GHz) = 2.56 ε_(r,||) (20° C., 19 GHz) = 3.68 tanδ_(εr,⊥) (20° C., 19 GHz) = 0.0075 tan δ_(εr,||) (20° C., 19 GHz) =0.0136 τ (20° C., 19 GHz) = 0.306 η (20° C., 19 GHz) = 22.5 Remark:t.b.d.: to be determined.

This mixture is suitable for applications in the microwave range, inparticular for phase shifters or LC based antenna elements in the microwave (MW) region. In comparison to the comparative example this mixtureclearly exhibits superior response times.

Example 21

A liquid-crystal mixture M-21 having the composition and properties asindicated in the following table is prepared and characterized withrespect to its general physical properties and its applicability inmicrowave components at 19 GHz.

Composition Compound Conc./ No Abbreviation mass-% 1 PU-3-S 20.0 2PVG-4-S 15.0 3 PVG-5-S 15.0 4 PTU-3-S 10.0 5 PGU-3-S 14.0 6 PPTU-4-S10.0 7 PPTU-5-S 10.0 Σ 100.0 Physical Properties T(N, I)/° C. = 96n_(o)(20° C., 589.3 nm) = t.b.d. Δn(20° C., 589.3 nm) = t.b.d.ε_(||)(20° C., 1 kHz) = 27.8 Δε(20° C., 1 kHz) = 5.0 γ₁ (20° C.)/mPa · s= 230 k₁ (20° C.)/pN = 15.6 k₃/k₁ (20° C.) = 1.00 V₀ (20° C.)/V = 0.88ε_(r,⊥) (20° C., 19 GHz) = 2.48 ε_(r,||) (20° C., 19 GHz) = 3.67 tanδ_(εr,⊥) (20° C., 19 GHz) = 0.0083 tan δ_(εr,||) (20° C., 19 GHz) =0.0152 τ (20° C., 19 GHz) = 0.324 η (20° C., 19 GHz) = 21.0 Remark:t.b.d.: to be determined.

This mixture is suitable for applications in the microwave range, inparticular for phase shifters or LC based antenna elements in the microwave (MW) region. In comparison to the comparative example this mixtureclearly exhibits superior response times.

Example 22

A liquid-crystal mixture M-22 having the composition and properties asindicated in the following table is prepared and characterized withrespect to its general physical properties and its applicability inmicrowave components at 19 GHz.

Composition Compound Conc./ No Abbreviation mass-% 1 PU-3-S 10.0 2PTU-3-S 10.0 3 PTU-5-S 10.0 4 CPU-2-S 20.0 5 CPU-5-S 20.0 6 PGU-3-S 16.07 PPTU-4-S 7.0 8 PPTU-5-S 7.0 Σ 100.0 Physical Properties T(N, I)/° C. =125 n_(o)(20° C., 589.3 nm) = t.b.d. Δn(20° C., 589.3 nm) = t.b.d.ε_(||)(20° C., 1 kHz) = 27.2 Δε(20° C., 1 kHz) = 4.6 γ₁ (20° C.)/mPa · s= 310 k₁ (20° C.)/pN = 14.1 k₃/k₁ (20° C.) = 1.44 V₀ (20° C.)/V = 0.85ε_(r,⊥) (20° C., 19 GHz) = t.b.d. ε_(r,||) (20° C., 19 GHz) = t.b.d. tanδ_(εr,⊥) (20° C., 19 GHz) = t.b.d. tan δ_(εr,||) (20° C., 19 GHz) =t.b.d. τ (20° C., 19 GHz) = t.b.d. η (20° C., 19 GHz) = t.b.d. Remark:t.b.d.: to be determined.

This mixture is suitable for applications in the microwave range, inparticular for phase shifters or LC based antenna elements in the microwave (MW) region. In comparison to the comparative example this mixtureclearly exhibits superior response times.

Example 23

A liquid-crystal mixture M-23 having the composition and properties asindicated in the following table is prepared and characterized withrespect to its general physical properties and its applicability inmicrowave components at 19 GHz.

Composition Compound Conc./ No Abbreviation mass-% 1 PU-3-S 10.0 2PTU-3-S 10.0 3 PTU-5-S 10.0 4 CPU-2-S 20.0 5 CPU-3-S 20.0 6 PGU-3-S 16.07 PPTU-4-S 7.0 8 PPTU-5-S 7.0 Σ 100.0 Physical Properties T(N, I)/° C. =124 n_(o)(20° C., 589.3 nm) = t.b.d. Δn(20° C., 589.3 nm) = t.b.d.ε_(||)(20° C., 1 kHz) = 27.8 Δε(20° C., 1 kHz) = 4.6 γ₁ (20° C.)/mPa · s= 301 k₁ (20° C.)/pN = 14.1 k₃/k₁ (20° C.) = 1.44 V₀ (20° C.)/V = 0.85ε_(r,⊥) (20° C., 19 GHz) = t.b.d. ε_(r,||) (20° C., 19 GHz) = t.b.d. tanδ_(εr,⊥) (20° C., 19 GHz) = t.b.d. tan δ_(εr,||) (20° C., 19 GHz) =t.b.d. τ (20° C., 19 GHz) = t.b.d. η (20° C., 19 GHz) = t.b.d. Remark:t.b.d.: to be determined.

This mixture is suitable for applications in the microwave range, inparticular for phase shifters or LC based antenna elements in the microwave (MW) region. In comparison to the comparative example this mixtureclearly exhibits superior response times.

Example 24

A liquid-crystal Mixture M-24 having the composition and properties asindicated in the following table is prepared and characterized withrespect to its general physical properties and its applicability inmicrowave components at 19 GHz.

Composition Compound Conc./ No Abbreviation mass-% 1 PU-3-S 10.0 2PTU-3-S 10.0 3 PTU-5-S 10.0 4 PGU-3-S 16.0 5 PPTU-4-S 7.0 6 PPTU-5-S 7.07 CPU-2-S 10.0 8 CPU-3-S 10.0 9 CPU-4-S 10.0 10  CPU-5-S 10.0 Σ 100.0Physical Properties T(N, I)/° C. = 127 n_(o)(20° C., 589.3 nm) = t.b.d.Δn(20° C., 589.3 nm) = t.b.d. ε_(||)(20° C., 1 kHz) = 27.1 ε_(⊥)(20° C.,1 kHz) = 4.5 γ₁ (20° C.)/mPa · s = 299 k₁ (20° C.)/pN = 14.8 k₃/k₁ (20°C.) = 1.43 V₀ (20° C.)/V = 0.86 ε_(r,⊥) (20° C., 19 GHz) = 2.35 ε_(r,||)(20° C., 19 GHz) = 3.44 tan δ_(εr,⊥) (20° C., 19 GHz) = 0.0116 tanδ_(εr,||) (20° C., 19 GHz) = 0.064 τ (20° C., 19 GHz) = 0.315 η (20° C.,19 GHz) = 27.2 Remark: t.b.d.: to be determined.

This mixture is suitable for applications in the microwave range, inparticular for phase shifters or LC based antenna elements in the microwave (MW) region. In comparison to the comparative example this mixtureclearly exhibits superior response times.

Example 25

A liquid-crystal mixture M-25 having the composition and properties asindicated in the following table is prepared and characterized withrespect to its general physical properties and its applicability inmicrowave components at 19 GHz.

Composition Compound Conc./ No Abbreviation mass-% 1 PU-3-S 8.0 2PVG-4-S 8.0 3 PVG-5-S 8.0 4 PTU-3-S 8.0 5 PTU-5-S 8.0 6 PGU-3-S 16.0 7PPTU-4-S 7.0 8 PPTU-5-S 7.0 9 CPU-3-S 10.0 10  CPU-4-S 10.0 11  CPU-5-S10.0 Σ 100.0 Physical Properties T(N, I)/° C. = 122 n_(o)(20° C., 589.3nm) = t.b.d. Δn(20° C., 589.3 nm) = t.b.d. ε_(||)(20° C., 1 kHz) = 26.2ε_(⊥)(20° C., 1 kHz) = 4.6 γ₁ (20° C.)/mPa · s = 298 k₁ (20° C.)/pN =16.0 k₃/k₁ (20° C.) = 1.31 V₀ (20° C.)/V = 0.91 ε_(r,⊥) (20° C., 19 GHz)= 2.36 ε_(r,||) (20° C., 19 GHz) = 3.48 tan δ_(εr,⊥) (20° C., 19 GHz) =0.0121 tan δ_(εr,||) (20° C., 19 GHz) = 0.0067 τ (20° C., 19 GHz) =0.321 η (20° C., 19 GHz) = 26.5 Remark: t.b.d.: to be determined.

This mixture is suitable for applications in the microwave range, inparticular for phase shifters or LC based antenna elements in the microwave (MW) region. In comparison to the comparative example this mixtureclearly exhibits superior response times.

Example 26

A liquid-crystal mixture M-26 having the composition and properties asindicated in the following table is prepared and characterized withrespect to its general physical properties and its applicability inmicrowave components at 19 GHz.

Composition Compound Conc./ No Abbreviation mass-% 1 PU-3-S 8.0 2PVG-4-S 8.0 3 PVG-5-S 8.0 4 PTU-3-S 8.0 5 PTU-5-S 8.0 6 PGU-3-S 16.0 7PPTU-4-S 7.0 8 PPTU-5-S 7.0 9 CPU-4-S 15.0 10  CPU-5-S 15.0 Σ 100.0Physical Properties T(N, I)/° C. = 124 n_(o)(20° C., 589.3 nm) = t.b.d.Δn(20° C., 589.3 nm) = t.b.d. ε_(||)(20° C., 1 kHz) = 26.2 ε_(⊥)(20° C.,1 kHz) = 4.6 γ₁ (20° C.)/mPa · s = 311 k₁ (20° C.)/pN = 16.2 k₃/k₁ (20°C.) = 1.28 V₀ (20° C.)/V = 0.91 ε_(r,⊥) (20° C., 19 GHz) = 2.37 ε_(r,||)(20° C., 19 GHz) = 3.48 tan δ_(εr,⊥) (20° C., 19 GHz) = 0.0120 tanδ_(εr,||) (20° C., 19 GHz) = 0.0066 τ (20° C., 19 GHz) = 0.318 η (20°C., 19 GHz) = 26.5 Remark: t.b.d.: to be determined.

This mixture is suitable for applications in the microwave range, inparticular for phase shifters or LC based antenna elements in the microwave (MW) region. In comparison to the comparative example this mixtureclearly exhibits superior response times.

The mixtures M-2 to M-26 are divided into two parts each. To each onethese two mixtures of the respective pairs alternatively 0.20% of S-1011and 0.40% of S-1011 are added, respectively, as in example 1 an theresultant mixtures are called M-1.1 and M-1.2 are investigated asdescribed under example 1.

The resultant mixtures show similarly improved properties as Examples1.1 and 1.2, in particular with regard to tunability and figure ofmerit.

Alternatively to the chiral compound S-1011 also its enantiomer can beused with the same improved effect(s). Also other chiral compounds, e.g.typical chiral dopants for liquid crystal mixtures ma y be beneficiallyused to achieve essentially the same effect(s).

1. Liquid-crystal medium, characterised in that it comprises one or morechiral compounds one or more compounds selected from the group ofcompounds of formulae I, II and III

in which R¹ denotes H, unfluorinated alkyl or unfluorinated alkoxyhaving 1 to 17 C atoms or unfluorinated alkenyl, unfluorinatedalkenyloxy or unfluorinated alkoxyalkyl having 2 to 15 C atoms, ndenotes 0 or 1, and

independently of one another, denote

alternatively denotes

in which R² denotes H, unfluorinated alkyl or unfluorinated alkoxyhaving 1 to 17 C atoms or unfluorinated alkenyl, unfluorinatedalkenyloxy or unfluorinated alkoxyalkyl having 2 to 15 C atoms, Z²¹denotes trans-CH═CH—, trans-CF=CF— or —C≡C—, and

independently of one another, denote

in which R³ denotes H, unfluorinated alkyl or unfluorinated alkoxyhaving 1 to 17 C atoms or unfluorinated alkenyl, unfluorinatedalkenyloxy or unfluorinated alkoxyalkyl having 2 to 15 C atoms, one ofZ³¹ and Z³² denotes trans-CH═CH—, trans-CF=CF— or —C≡C— and the otherone, independently thereof, denotes trans —CH═CH—, trans-CF=CF— or asingle bond, and

independently of one another, denote

alternatively independently denotes e

 and optionally one or more polymerisable compounds preferably offormula PP^(a)—(Sp^(a))_(s1)-(A¹-Z¹)_(n1)-A²-Q-A³-(Z⁴-A⁴)_(n2)-(Sp^(b))_(s2)-P^(b)  Pwherein the individual radicals have the following meanings: P^(a),P^(b) each, independently of one another, are a polymerisable group,Sp^(a), Sp^(b) each, independently of one another, denote a spacergroup, s1, s2 each, independently of one another, denote 0 or 1, n1, n2each, independently of one another, denote 0 or 1, preferably 0, Qdenotes a single bond, —CF₂O—, —OCF₂—, —CH₂O—, —OCH₂—, —(CO)O—, —O(CO)—,—(CH₂)₄—, —CH₂—CH₂—, —CF₂—CF₂—, —CF₂—CH₂—, —CH₂—CF₂—, —CH═CH—, —CF=CF—,—CF=CH—, —(CH₂)₃O—, —O(CH₂)₃—, —CH═CF—, —C≡C—, —O—, —CH₂—, —(CH₂)₃—,—C₂—, preferably —CF₂O—, Z¹, Z⁴ denote a single bond, —CF₂O—, —OCF₂—,—CH₂O—, —OCH₂—, —(CO)O—, —O(CO)—, —(CH₂)₄—, —CH₂—CH₂—, —CF₂—CF₂—,—CF₂—CH₂—, —CH₂—CF₂—, —CH═CH—, —CF=CF—, —CF=CH—, —(CH₂)₃O—, —O(CH₂)₃—,—CH═CF—, —C≡C—, —O—, —CH₂—, —(CH₂)₃—, —CF₂—, where Z¹ and Q or Z⁴ and Qdo not simultaneously denote a group selected from —CF₂O— and —OCF₂—,A¹, A², A³, A⁴ each, independently of one another, denote a diradicalgroup selected from the following groups: a) the group consisting oftrans-1,4-cyclohexylene, 1,4-cyclohexenylene and 1,4′-bicyclohexylene,in which, in addition, one or more non-adjacent CH₂ groups may bereplaced by —O— and/or —S— and in which, in addition, one or more Hatoms may be replaced by F, b) the group consisting of 1,4-phenylene and1,3-phenylene, in which, in addition, one or two CH groups may bereplaced by N and in which, in addition, one or more H atoms may bereplaced by L, c) the group consisting of tetrahydropyran-2,5-diyl,1,3-dioxane-2,5-diyl, tetrahydrofuran-2,5-diyl, cyclobutane-1,3-diyl,piperidine-1,4-diyl, thiophene-2,5-diyl and selenophene-2,5-diyl, eachof which may also be mono- or polysubstituted by L, d) the groupconsisting of saturated, partially unsaturated or fully unsaturated, andoptionally substituted, polycyclic radicals having 5 to 20 cyclic Catoms, one or more of which may, in addition, be replaced byheteroatoms, preferably selected from the group consisting ofbicyclo[1.1.1]pentane-1,3-diyl, bicyclo[2.2.2]octane-1,4-diyl,spiro[3.3]heptane-2,6-diyl,

 where, in addition, one or more H atoms in these radicals may bereplaced by L, and/or one or more double bonds may be replaced by singlebonds, and/or one or more CH groups may be replaced by N, and A³,alternatively may be a single bond, L on each occurrence, identically ordifferently, denotes F, Cl, CN, SCN, SF₅ or straight-chain or branched,in each case optionally fluorinated, alkyl, alkoxy, alkylcarbonyl,alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy having 1 to 12 Catoms, R⁰³, R⁰⁴ each, independently of one another, denote H, F orstraight-chain or branched alkyl having 1 to 12 C atoms, in which, inaddition, one or more H atoms may be replaced by F, M denotes —O—, —S—,—CH₂—, —CHY¹— or —CY¹Y²—, and Y¹ and Y² each, independently of oneanother, have one of the meanings indicated above for R⁰, or denote Clor CN, and one of the groups Y¹ and Y² alternatively denotes —OCF₃,preferably H, F, Cl, CN or CF₃.
 2. Liquid-crystal medium according toclaim 1, characterised in that it comprises one or more chiral compoundshaving an absolute value of the HTP of 10 μm or more.
 3. Liquid-crystalmedium according to claim 2, characterised in that it comprises one ormore chiral compounds selected from the group of compounds of formulaeA-I to A-VI:

including the (R,S), (S,R), (R,R) and (S,S) enantiomers, which are notshown,

in which R^(a11) and R^(a12), independently of one another, are alkyl,oxaalkyl or alkenyl having from 2 to 9 carbon atoms, and R^(a11) isalternatively methyl or alkoxy having from 1 to 9 carbon atoms, R^(a21)and R^(a22), independently of one another, are alkyl or alkoxy havingfrom 1 to 9 carbon atoms, oxaalkyl, alkenyl or alkenyloxy having from 2to 9 carbon atoms, R^(a31) and R^(a32), independently of one another,are alkyl, oxaalkyl or alkenyl having from 2 to 9 carbon atoms, andR^(a11) is alternatively methyl or alkoxy having from 1 to 9 carbonatoms,

are each, independently of one another, 1,4-phenylene, which may also bemono-, di- or trisubstituted by L, or 1,4-cyclohexylene, L is H, F, Cl,CN or optionally halogenated alkyl, alkoxy, alkylcarbonyl,alkoxycarbonyl or alkoxycarbonyloxy having 1-7 carbon atoms, c is 0 or1, Z⁰ is —COO—, —OCO—, —CH₂CH₂— or a single bond, and R⁰ is alkyl,alkoxy, alkylcarbonyl, alkoxycarbonyl or alkylcarbonyloxy having 1-12carbon atoms. X¹, X², Y¹ and Y² are each, independently of one another,F, Cl, Br, I, CN, SCN, SF₅, straight-chain or branched alkyl having from1 to 25 carbon atoms, which may be monosubstituted or polysubstituted byF, Cl, Br, I or CN and in which, in addition, one or more non-adjacentCH₂ groups may each, independently of one another, be replaced by —O—,—S—, —NH—, NR⁰—, —CO—, —COO—, —OCO—, —OCOO—, —S—CO—, —CO—S—, —CH═CH— or—C≡C— in such a way that O and/or S atoms are not bonded directly to oneanother, a polymerisable group or cycloalkyl or aryl having up to 20carbon atoms, which may optionally be monosubstituted or polysubstitutedby halogen or by a polymerisable group, x¹ and x² are each,independently of one another, 0, 1 or 2, y¹ and y² are each,independently of one another, 0, 1, 2, 3 or 4, B¹ and B² are each,independently of one another, an aromatic or partially or fullysaturated aliphatic six-membered ring in which one or more CH groups maybe replaced by N atoms and one or more non-adjacent CH₂ groups may bereplaced by O and/or S, W¹ and W² are each, independently of oneanother, —Z¹-A¹-(Z²-A²)_(m)-R, and one of the two is alternatively R¹ orA³, but both are not simultaneously H, or

U¹ and U² are each, independently of one another, CH₂, O, S, CO or CS,V¹ and V² are each, independently of one another, (CH₂)_(n), in whichfrom one to four non-adjacent CH₂ groups may be replaced by O and/or S,and one of V¹ and V² and, in the case where

both are a single bond, Z¹ and Z² are each, independently of oneanother, —O—, —S—, —CO—, —COO—, —OCO—, —O—COO—, —CO—NR⁰—, —NR⁰—CO—,—O—CH₂—, —CH₂—O—, —S—CH₂—, —CH₂—S—, —CF₂—O—, —O—CF₂—, —CF₂—S—, —S—CF₂—,—CH₂—CH₂—, —CF₂—CH₂—, —CH₂—CF₂—, —CF₂—CF₂—, —CH═N—, —N═CH—, —N═N—,—CH═CH—, —CF=CH—, —CH═CF—, —CF=CF—, —C≡C—, a combination of two of thesegroups, where no two O and/or S and/or N atoms are bonded directly toone another, or a single bond, A¹, A² and A³ are each, independently ofone another, 1,4-phenylene, in which one or two non-adjacent CH groupsmay be replaced by N, 1,4-cyclohexylene, in which one or twonon-adjacent CH₂ groups may be replaced by O and/or S,1,3-dioxolane-4,5-diyl, 1,4-cyclohexenylene, 1,4-bicyclo[2.2.2]octylene,piperidine-1,4-diyl, naphthalene-2,6-diyl, decahydronaphthalene-2,6-diylor 1,2,3,4-tetrahydronaphthalene-2,6-diyl, where each of these groupsmay be monosubstituted or polysubstituted by L, and in addition A¹ is asingle bond, L is a halogen atom, CN, NO₂, alkyl, alkoxy, alkylcarbonyl,alkoxycarbonyl or alkoxycarbonyloxy having 1-7 carbon atoms, in whichone or more H atoms may be replaced by F or Cl, m is in each case,independently, 0, 1, 2 or 3, and R and R¹ are each, independently of oneanother, H, F, Cl, Br, I, CN, SCN, SF₅, straight-chain or branched alkylhaving from 1 or 3 to 25 carbon atoms respectively, which may optionallybe monosubstituted or polysubstituted by F, Cl, Br, I or CN, and inwhich one or more non-adjacent CH₂ groups may be replaced by —O—, —S—,—NH—, —NR⁰—, —CO—, —COO—, —OCO—, —O—COO—, —S—CO—, —CO—S—, —CH═CH— or—C≡C—, where no two O and/or S atoms are bonded directly to one another,or a polymerisable group.
 4. Liquid-crystal medium according claim 1,characterised in that it comprises one or more compounds of the formulaI, as indicated in claim
 1. 5. Liquid-crystal medium according to claim1, characterised in that it comprises one or more compounds of formulaII, as indicated in claim
 1. 6. Liquid-crystal medium according to claim1, characterised in that it comprises one or more compounds of formulaeIII, as indicated in claim
 1. 7. Liquid-crystal medium according toclaim 1, characterised in that it comprises one or more compoundsselected from the group of compounds of formulae I-1, I-2, II-1 to II-3and III-1 to III-6

in which the parameters have the respective meanings given in claim 1.8. Liquid-crystal medium according to claim 1, characterised in that itcomprises a polymerizable compound and optionally additionally comprisesa polymerisation initiator.
 9. Method of improving the response time ofa liquid-crystal medium according claim 1 by using one or more chiralcompounds.
 10. Composite system comprising a polymer obtained from thepolymerisation of a polymerisable compound and a polymerizationinitiator a liquid-crystal medium comprising one or more chiralcompounds and one or more compounds selected from the group of compoundsof formulae I to III, as specified in claim
 1. 11. Component forhigh-frequency technology, characterised in that it comprises a liquidcrystal medium according to claim
 1. 12. Component according to claim11, characterised in that it is suitable for operation in the microwaverange.
 13. Component according to claim 11, characterised in that it isa phase shifter or a LC based antenna element operable in the microwaveregion.
 14. A method which comprises including a liquid-crystal mediumaccording to claim 1 in a component for high-frequency technology. 15.Process for the preparation of a liquid-crystal medium, characterised inthat one or more chiral compounds are mixed with one or more compoundsselected from the group of the compounds of the formulae I, II and III,as specified in claim 1, and optionally with one or more furthercompounds and/or with one or more additives.
 16. Microwave antennaarray, characterised in that it comprises one or more componentsaccording to claim 11.